Convex photos on Flickr

Shell-exterior cannot be relied on, and shell-interiors can be confusing. Examination, in good light under magnification, of extended pallial tentacles on living animals is essential for consistent accurate discrimination of the three rock-dwelling Patella species. Best achieved with specimen adhering to underside of supported glass-sheet in black-based container of seawater.

Some morphologically intermediate forms can only be reliably identified by sequencing DNA or allozyme study 36Pd flic.kr/p/BdwtN8 and 37Pd flic.kr/p/AzydCD . Intermediates result from similar environmental factors affecting different species in similar ways and are not hybrids (Sanna et al., 2011 and Sá-Pinto et al., 2007). For the purpose of recording for distribution schemes it is advisable to disregard intermediates unless DNA or allozymes can be employed, especially beyond or on the limits of known distributions. Intermediates most frequent near limit of distributions of P. depressa and P. ulyssiponensis in Isle of Wight , perhaps because conditions not optimal (Fretter and Graham, 1994).

Key identification features of typical British specimens.

Patella depressa

[1&2 in combination, not singly, diagnostic of typical specimens but excludes intermediates.]

1. Pigmented pallial tentacles are opaque chalky-white for more than half of extended-length; may have translucent tip; distinctly whiter than buff mantle-skirt from which they arise 19Pd flic.kr/p/Af37zY . Even when mantle-skirt retracted, pallial tentacles often clearly visible contrasting with the darker mantle17Pd flic.kr/p/BaRWfU .

2. Sole of foot pitch-brown 16Pd flic.kr/p/Afb9yv to black 17Pd flic.kr/p/BaRWfU .

3. On shell-interior, whitish projecting points of ribs have short, unglazed, chalky, pure-white central line, but reduced or lacking where projecting points of ribs eroded 8Pd flic.kr/p/Ay6YL9 . [This feature recently recognised by S. Payne, and applies to all in large sample examined by IFS. ]

Before making records of this species further north than NW Anglesey it is advisable to familiarize oneself with specimens in areas where it is known to be frequent such as S. Devon, Channel Islands or Brittany.

Confirmation/correction can be sought by posting clear photo of pallial tentacles and foot on British Marine Molluscs Group at www.facebook.com/groups/british.marine.mollusca/

Similar species

Patella ulyssiponensis

1. Pallial tentacles have opaque pigment; white, off-white, cream or, on large specimens, yellowish or orange for about half of length; distal-half fades to translucent. Opaque basal parts often distinct from translucent mantle-skirt that they arise from so possible to confuse with P. depressa; important to use pallial tentacles in combination with foot-colour/shell-length for identification 41Pd flic.kr/p/ABFYRn .

2. Foot not pitch-brown/black; whitish when young 42Pd flic.kr/p/ALnSTW becoming yellowish 43Pd flic.kr/p/Ber2rm and often orange with age 44Pd flic.kr/p/ALnJ39 . Beware of juveniles under 12mm length that lack gonads above sole as dark viscera may show as blackish-shadow through thin pale translucent foot 42Pd flic.kr/p/ALnSTW . Green ovaries resting on interior surface of foot of mature female may show as faint greenish tinted zone along median line of foot where it is thinnest 43Pd flic.kr/p/Ber2rm .

Patella vulgata

Extremely variable species; foot colours and nearly all shell-features have overlaps with P. depressa and P. ulyssiponensis.

1. Pigment-less pallial tentacles are slender, translucent and same colour as mantle-skirt they arise from 45Pd flic.kr/p/AiLHRg .

Cautions:

Pallial tentacles may look white when arise from colourless mantle-skirt in some lighting, but no pigment and not chalky-white 46Pd flic.kr/p/AE15Wx .

Pigment-less translucency and fineness often make discernment difficult, especially when mantle skirt retracted from shell-rim and pallial tentacles viewed against shell 47Pd flic.kr/p/BeqQNY ; often virtually invisible when out of water as may be retracted into mantle 48Pd flic.kr/p/ABFF5R .

Foot colour varies, sometimes as dark as on P. depressa 47Pd flic.kr/p/BeqQNY .

Habits and ecology

On rocky shores with mild winters (January mean air temperature 42°F/5.6°C and above 40Pd flic.kr/p/BewPND ) with Ballantine (1961) wave exposure scale 1-5 (extremely exposed to fairly sheltered) where turbidity does not prevent plant growth. On bedrock in shallow pools, seawater trickles or other damp positions, not on shingle or boulders. Not sublittoral; lower limit varies, usually somewhere between MLWN and MLWS; upper limit MHWN, or EHWS if frequent swell-splash or in pools. Average size of adults decreases up shore (Branch, 1981a); unable to produce very large, thick, high-domed shells, like those of some P. vulgata 49Pd flic.kr/p/ABGb4o , to resist dessication on drained rock on upper shore, though some intermediate forms show a tendency towards a high profile 36Pd flic.kr/p/BdwtN8 . P.depressa is reported to be a rigidly homing species (Branch, 1981a), adults always after feeding-excursions seeking to return to same position. Foot longitudinally divided on interior by deep median groove of large blood sinus 25Pd flic.kr/p/ABS7Sp . Locomotion by retrograde waves alternating on each side (ditaxic) of sole; muscles alternately compress/relax against blood trapped between them to create waves 25Pd flic.kr/p/ABS7Sp . Feeds, mainly at night (Branch, 1981a) , on algal sporelings, detritus containing diatoms and organic remains, and on short algal growths, including encrusting calcareous spp. Grazing rock surfaces is facilitated by powerful muscles on large buccal mass 32Pd flic.kr/p/Bcivym , and by hard, iron-mineralized teeth on long ribbon with plentiful replacements for worn teeth 33Pd flic.kr/p/ABRUWR . Length varies seasonally; shorter when wear of active feeding exceeds growth rate. Patella spp. wear out up to two rows of teeth per day (Sigel, 2008 ). About four rows of teeth are in contact with substrate during feeding 15Pd flic.kr/p/Ay6H2J ; loose particles are retained by rim of surrounding jaw# 24Pd flic.kr/p/BdwNkP and the licker 32Pd flic.kr/p/Bcivym which sweeps them up at the end of the radula stroke. Long coiled intestine 30Pd flic.kr/p/Bex7R6 compacts faeces into firm faecal strings that will not contaminate gills in pallial groove; compensates for adults lacking hypobranchial gland to produce mucus to bind particles exiting from nuchal cavity. Cilia on roof of nuchal cavity and side of foot conduct faecal matter from anus in nuchal cavity to middle of right side 38Pd flic.kr/p/AguFeC . Faeces and debris accumulate there until periodic sharp contraction of pedal-retractor muscle clamps shell down and forcefully flushes water and waste out of shell (Fretter & Graham 1962 & 1994). When limpets removed from rock, accumulated pile of faecal strings often found in position. Cilia also create inhalent water-current from left of head through nuchal cavity, where urogenital openings located, and thence carry excreta and ova/sperm to exterior. Predators reported to be able to dislodge P. vulgata shells probably take P. depressa too; they include gulls (Larus spp.), oystercatchers (Haematopus ostralegus), crabs, starfish and rats. Nucella lapillus bores through the shell, usually to the pedal-retractor muscle where the adjacent viscera are accessible obliquely to its radula without having to bore through the thick amphora# shell-layers covering the viscera. Boring takes several days, but is rewarded with a large food supply, providing the Nucella isn't dislodged before completion 39Pd flic.kr/p/AguCY5 . Absence or scarcity of P.depressa from very sheltered sites, where crabs are abundant, and from the sublittoral fringe, where starfish occur, might be because of greater susceptibilty of this small species to them than of the larger P. vulgata and P. ulyssiponensis. Respiration: gill-cilia create gentle local inhalent respiratory water currents all around perimeter of animal from adjacent shell-rim onto gills, and exhalent currents below gills back to shell-rim 38Pd flic.kr/p/AguFeC (Yonge & Thompson, 1976). Densely ciliated groove on stalk and rim of each gill-lamella catches and removes large particles of detritus that would clog gill (Fretter & Graham, 1994) 18Pd flic.kr/p/Bc59v8 . Blood passes from viscera and foot via vessels through gaps in encircling shell-muscle 20Pd flic.kr/p/Ay6PEH into gills for oxygenation, and thence into encircling efferent pallial vessel 26Pd flic.kr/p/BciErS which takes it through nuchal cavity 29Pd flic.kr/p/AguVDE to heart for recirculation to head, foot and viscera (Fretter & Graham, 1994) .

Breeds spring to autumn, perhaps with summer pause (Fretter & Graham, 1994). May vary geographically; Yonge & Thompson (1976) said breeds sporadically all year with summer maximum. External fertilization so close proximity of sexes required for success; new populations unlikely to be established by isolated strays. Sperm and ova shed into water column, ova individually. Eggs hatch as free trochophore larvae (stage passed within egg by most “less-primitive” spp.) in plankton before transforming to veligers and, after a short planktonic-life, settling on lower shore and assuming limpet form. Spat, when 1mm long, have ten radiating ridges; P. vulgata has five ridges on right, four on left. P. ulyssiponensis has eight (Fretter & Graham, 1994). Move higher up shore when shell-length 5mm.

Distribution and status

P. depressa is a North-east Atlantic species extending northwards from Senegal (Trigo et al., 2018) through western Iberia and France to its northern limits in North Wales, eastern part of south coast England and Normandy. It extends only a short way into the Mediterranean. Trigo et al. (2018) states to Malaga, but an image with diagnostic foot and pallial tentacles shows it extends to Almeira 51Pd flic.kr/p/2k6xwit . Its absence further into the Mediterranean might be because the slight tidal rise and fall there does not produce a sufficient intertidal zone for this purely eulittoral species. The precise northern limits fluctuate, generally polewards in warm periods and receding in cooler periods, though other factors may have an influence 40Pd flic.kr/p/BewPND . In Britain, it is restricted to areas with mild winters with February mean Sea Surface Temperatures above 8°C. Consistently present populations occur between the Isle of Wight and mid Wales with zones of fluctuation beyond those points (Kendall et al. 2004). The most recent published information (Oróstica et al., October 2020 ) shows that, as would be expected in this period of exceptional temperature increase, the range has extended with scattered rare specimens reaching Beachy Head in south-east England, near Dunster in Somerset and Barry in Glamorgan but, unexpectedly, it has not reoccupied the north-western side of Lleyn or north-west Anglesey where it was recorded in the 1950s and lost in the 1980s.

The absence of P. depressa records on the mild-winter coasts of Ireland obviously requires explanation. Its distribution is used in Lewis (1964) as an exemplar of “southern species” with an explanation for its absence from Ireland. This eulittoral species cannot crawl across wide sublittoral areas. It is possible that it reached Britain in the warming after the Ice Age before sea-level rise cut Britain off from the continent but after Ireland had been cut off from Britain. Planktonic larvae can traverse sublittoral areas, but the phase is short in P. depressa so time is limited and it is difficult if currents are adverse. External fertilization requires a minimum population density with the sexes in close proximity for successful establishment of a sustained population; there may have been occasional small settlements in Ireland that have subsequently failed (Lewis, 1964). Records in Ireland, Scotland and the North Sea on distribution maps should be regarded as misidentifications unless there is photographic evidence of both brown-black foot and chalk-white opaque pallial tentacles.

Acknowledgements

I gratefully acknowledge the help of Jan Light and Sebastian Payne with information and discussion, and in providing many specimens for examination. Any errors or omissions are the responsibility of the author. I thank Samuel Santos García for use of his photograph of a specimen from Almeira.

Links and references

Akşit, D. & Falakil Mutaf, B. 2011. The external morphology of the gill of Patella caerulea L. (Mollusca: Gastropoda). Turk. J. Zool. 35(4) 603-606. Tübitak. Turkey. PDF contains SEM images of gill lamellae.

www.google.co.uk/search?q=patella+gill+ciliated+groove&am...

Ballantine, W.J. 1961. A biologically-defined exposure scale for comparative description of rocky shores. Field studies 1(3): 1-19. Free pdf at: fsj.field-studies-council.org/media/344345/vol1.3_17.pdf

Barber, A.H., Lu, D. & Pugno, N.M. 2015 Extreme strength observed in limpet teeth The Royal Society.

rsif.royalsocietypublishing.org/content/12/105/20141326

Branch, G.M. 1981a. The biology of limpets. Oceangr. Mar. Biol. Ann. Rev. learning.watfordboys.org/mod/resource/view.php?id=4730

Branch, G.M. 1981b. The biology of limpets. Oceangr. Mar. Biol. Ann. Rev. www.google.co.uk/search?q=Patella+vulgata+blood+circulati...

Cohen, A.L. & Branch, G.M. 1992. Environmentally controlled variation in the structure and mineralogy of Patella granularis shells from the coast of southern Africa: implications for palaeotemperature assessments. Palaeogeography, palaeoclimatology, palaeoecology, 91: 49-57. www.whoi.edu/fileserver.do?id=163844&pt=2&p=36767

Forbes, E. & Hanley S. 1849-53. A history of the British mollusca and their shells. vol. 2 (1849), London, van Voorst. (As dark-bodied variety of their P. athletica) ; Free PDF at archive.org/stream/historyofbritish02forb#page/428/mode/2up Use slide at base of page to select pp.428 for footnote.

Fretter, V. and Graham, A. 1962. British prosobranch molluscs. London, Ray Society.

Fretter, V. and Graham, A. 1994. British prosobranch molluscs. Revised and updated edition. London, Ray Society.

Goshima, S., Ilano A.S. & Ito, A. 2002. Seasonal and tidal-height variations in body weight and radular length in Nodilittorina radiata (Eydoux & Souleyet, 1852) J. Mollus. Stud. 68(3): 197-203.

mollus.oxfordjournals.org/content/68/3/197.full.pdf+html

Graham, A. 1988. Prosobranch and pyramidellid gastropods. London.

Heppel, D. 1964. Recorder's report: marine Molluscs. J. Conch. Lond., 25: 308-313.

Hughes, S.L., Holliday, N.P., Kennedy, J., Berry, D.I., Kent, E.C., Sherwin, T., Dye, S., Inall, M., Shammon, T. and Smyth, T. 2010. Temperature (Air and Sea) in MCCIP Annual Report Card 2010-11, MCCIP Science Review, 16pp. www.mccip.org.uk/arc

Jeffreys, J.G. 1862-69. British conchology. vol. 3 (1865). London, van Voorst. (As var.3 intermedia of Patella vulgata. Note that var.4 depressa describes P. ulyssiponensis features); Free PDF at archive.org/stream/britishconcholog03jeff#page/230/mode/2up . Use slide at base of page to select pp.230- 241.

Lewis, J.R. 1964. The ecology of rocky shores. London, Hodder & Stoughton.

Light, J. A guide to limpet identification for the general naturalist www.glaucus.org.uk/Limpet.htm

MacClintock, C. 1967. Shell structure of patelloid and bellerophontid gastropods (Mollusca). Peabody Museum of Natural History, Yale University. Bulletin 22.pdf at

www.google.co.uk/?gws_rd=ssl#q=MacClintock%2C+C.+1967.+Sh....

215 pages, may take a few minutes to download. Contents on page v.(= p.6 of pdf). To find pages on pdf add 1 to Roman numerals, and add 11 to Arabic numerals.

McKay, D.W. and Smith, S.M. 1979. Marine mollusca of East Scotland. Edinburgh, Royal Scottish Museum.

Moore, H.B. 1937. Marine fauna of the Isle of Man. University Press of Liverpool. (“P. depressa Pennant” listed for I.O.M., but “[= P. athletica Bean] Forbes & Hanley 1853” shows record is actually of P. ulyssiponensis following the taxonomic misunderstanding of Jeffreys, and Forbes & Hanley).

Oróstica, M. H 2018. Living at the edge: Ecology of Patella species in Britain. PhD thesis. Bangor University.

research.bangor.ac.uk/portal/files/22310847/2018OrosticaP...

Oróstica, M. H., Hawkins, S. J., Broitman, B. R. and Jenkins S. R. 2020. Performance of a warm-water limpet species towards its poleward range edge compared to a colder-water congener. Mar Ecol Prog Ser doi.org/10.3354/meps13461

Pennant, T. 1777 British zoology London.

Page 142 biodiversitylibrary.org/item/127011#page/168/mode/1up

Pl. 89 fig.146. biodiversitylibrary.org/item/127011#page/361/mode/1up

Sanna, D., Dedola, G. L., Lai, T., Curini-Galletti, M. & Casu, M. 2011. PCR-RFLP: A practical method for the identification of specimens of Patella ulyssiponensis s.l. (Gastropoda: Patellidae), Italian Journal of Zoology,

pdf at www.researchgate.net/publication/233126771_PCR-RFLP_A_pra...

Sá-Pinto, A., Branco,M., Harris, D.J. & Alexandrino, P. 2005. Phylogeny and phylogeography of the genus Patella based on mitochondrial DNA sequence data. J. Exp. Mar. Biol. Ecol. 325: 95-110.

Sá-Pinto, A., Alexandrino, P. & Branco,M. 2007. High genetic differentiation with no evidence of hybridization between four limpet species (Patella spp.) revealed by allozyme loci. Scientia Marina 71(4): 801-810. Barcelona. pdf at www.vliz.be/imisdocs/publications/131981.pdf

Sigel, A., Sigel, H. and Sigel, R.K.O., (Editors) 2008. Biomineralization: from nature to application. Chichester, Wiley. Page 299 (to access this page on-line Google-search “limpet wear teeth” and scroll down results to find title) books.google.co.uk/books?id=TiwK2VQhPMkC&pg=PA299&amp...

Tomlin, J.R.Le B. 1923. Patella depressa Pennant. J. Conch. Lond., 17: 34.

Trigo, J.E.; Diaz Agras, G.J.; Garcia Alvarez, O.L.; Guerra, A.; Moreira, J.; Pérez, J.; Rolán, E.; Troncoso, J.S,; Urgorri, V.. 2018. Guia de los Moluscos Marinos de Galicia. Servicio de Publicacións da Universidade de Vigo.

Yonge, C.M. and Thompson, T.E. 1976. Living marine molluscs. London.

Current taxonomy: World Register of Marine Species (WoRMS)

www.marinespecies.org/aphia.php?p=taxdetails&id=151374

GLOSSARY

amphora – (on interior of limpet shell) Roman amphora-shaped area enclosed by scars of pedal-retractor muscle and anterior mantle-attachment.

aperture – mouth of gastropod shell; outlet for head and foot.

apex - earliest formed part of a gastropod shell, the summit of the cone. (In this limpet-account restricted to the exterior of the shell, and “vertex” used for the interior.)

cephalic – (adj.) of or on the head.

cilia – (pl.) microscopic linear extensions of membrane that move in rhythmic waves to create locomotion, or move particles and liquids e.g. inhalent water currents. (“cilium” singular). (Electron scanning microscope image at flic.kr/p/qQB5zj )

ciliary – (adj.) relating to or involving cilia.

coll. – in the collection of (named person or institution) (compare with legit).

conoid – shaped like a cone.

ctenidium – comb-like molluscan gill; usually an axis with a row of filaments either side (missing from Patella spp.).

distal - away from centre of body or point of attachment.

ditaxic - (of locomotion waves on foot) double series of waves, out of phase with each other, one series on each side of median line on sole.

ELWS – extreme low water spring tide level (usually near March and September equinoxes).

EHWS - extreme high water spring tide level (usually near March and September equinoxes).

epipodial - (adj.) of the epipodium (collar or circlet running round sides of foot of some gastropods).

epithelium – membranous covering of internal and external surfaces of animal's body, e.g. skin and lining of tubes and cavities.

head scar – term used by many British authors for patch of different shell-material, and often different colour, near vertex of interior of limpet shell; misnomer as the mobile head, free of any attachment to the shell or mantle-roof of the nuchal cavity cannot make a scar. A preferable term is “vertex patch”.

height – (of limpet) perpendicular distance from apex to plane of aperture-rim (best measured with callipers).

hyaline shield – transparent sheet of chitin at anterior of radula that rests on bolsters of odontophore; attachment point for retractor muscles of radula; helps guide food particles into mouth.

interspecific – existing or arising between different species.

intraspecific – occuring within a single species or involving members of one species.

jaw - unarticulated chitinous structure that encloses inner lips of Patella spp. at sides and anterior.

legit – (abbreviation; leg.) collected/ found by (compare with coll.)

licker - cuticularized structure with plate-like ridges and deep transverse grooves at tip of radula of Patella spp.; retains and sweeps up food particles.

mantle – sheet of tissue covering visceral mass of molluscs. Secretes shell of shelled species, and forms part or all of dorsal body surface (notum) of those without shells. (See mantle skirt.)

mantle skirt – extension on gastropods of mantle proper as a flap roofing a cavity containing gills, genital and renal openings, anus etc. On limpets, skirt and cavity extend around periphery of animal.

MHWN - mean high water neap tide level (mean level reached by weakest high tides for a few days every fortnight. i.e. those that rise the least).

MLWN – mean low water neap tide level (mean level reached by weakest low tides for a few days every fortnight. i.e. those that fall the least).

MLWS - mean low water spring tide level (mean level reached by lowest low tides for a few days every fortnight; Laminaria or Coralline zone on rocky coasts).

nuchal – (adj.) of nape of the neck.

nuchal cavity – cavity roofed by mantle skirt that contains head of limpet; part of mantle cavity (remainder consists of pallial groove on each side of body).

ovoid – egg-shaped, as a solid or in outline.

pallial groove band – shell material deposited on interior of shell by strip of black mantle roofing the pallial groove that contains the gills. On British Patella spp. p.g. band is often clouded-white.

pedal retractor muscle – strong muscle that retracts foot into shell of most gastropods, but on limpets is used to clamp shell to substrate, a.k.a. “foot muscle”.

retrograde - (of locomotion waves on foot) waves travel from anterior to posterior.

scar – mark on shell made by attachment point of muscle or other body part.

skirt shell layer - shell material deposited on interior of shell by mantle skirt. On British Patella spp. colourless when deposited, and clouded white, or transparent showing the colours of the outer layer. Crystalline structure causes short lines of blue iridescence parallel to the aperture rim on all four British species of Patella when the light is right.

trochophore – spherical or pear-shaped larva that swims with aid of girdle of cilia. Stage preceding veliger, passed within gastropod egg in most spp. but free in plankton for patellid limpets, most Trochidae and Tricolia pullus.

tricuspid - (of tooth) having three points.

unicuspid - (of tooth) having a single point.

veliger – shelled larva of marine gastropod or bivalve mollusc which moves by beating cilia of a velum (bilobed flap).

vertex – angle at highest point on interior of limpet-shell. [Synonym of “apex”, chosen (by IFS) to help avoid confusion with the highest point, apex, on the exterior. Gmelin used “vertex” when describing the interior of Patella ulyssiponensis, and in classical Latin “vertex” was used for the “pole of the heavens”; obviously only seen from below.]

vertex patch –layer of different shell-material, and often different colour, at vertex of interior of limpet shell. (See “head scar”.)

Gray whale fluke by Julia Sumangil

11 3

"Proportionately large tail flukes with convex, ragged trailing edge (notch in centre with pointed tips)."

"grey body, marbled and blotched (scarred)paler, with numerous pale barnacles and small parasitic crustaceans encrusted."

The gray whale (Eschrichtius robustus),[1] also known as the grey whale,[3] gray back whale, Pacific gray whale, or California gray whale[4] is a baleen whale that migrates between feeding and breeding grounds yearly. It reaches a length of 14.9 meters (49 ft), a weight of 36 tonnes (40 short tons), and lives between 55 and 70 years.[5] The common name of the whale comes from the gray patches and white mottling on its dark skin.[6] Gray whales were once called devil fish because of their fighting behavior when hunted.[7] The gray whale is the sole living species in the genus Eschrichtius, which in turn is the sole living genus in the family Eschrichtiidae. This mammal descended from filter-feeding whales that appeared at the beginning of the Oligocene, over 30 million years ago. Source: en.wikipedia.org/wiki/Gray_whale

01 Tritia nitida COMPARISON T. reticulata by Morddyn

9

Comparison of (on left) T. nitida, height 26.3 mm, with T. reticulata, height 27.2 mm.

Beached shells collected together from Blackwater Estuary, Essex, England in September 2019 by S. Taylor.

Recognition of Tritia nitida (Jeffreys, 1867) in Britain and Ireland.

Ian F. Smith (text) and Simon Taylor (fieldwork).

A pdf of this article can be downloaded from www.researchgate.net/publication/336441072_Recognition_of...

[Click 'file available' and then 'download'.]

Odd numbers for T. nitida. Even numbers for T. reticulata sensu stricto (Linnaeus, 1758).

1: spire whorls convex. (Tumidity of T. nitida varies in Mediterranean.)

2: spire whorls almost flat.

3: translucent parietal lip exposes colour of underlying body whorl. (Occasionally opaque in Mediterranean.)

4: opaque white parietal lip, semicircular, conceals colour of body whorl.

5: protoconch eroded on this one and nearly all T. nitida in sample. (Generally eroded on live T. nitida in Ria de Vigo.)

6: protoconch intact. (Generally intact on T. reticulata in Ria de Vigo.)

7: siphonal canal meets palatal lip at obtuse angle (120° in this case).

8: siphonal canal meets palatal lip at acute or right angle (80° in this case).

(Angle on both species alters if eroded; fresh unworn shells required.)

Tritia nitida was first described by Jeffreys (1867) from the muddy estuaries of the Thames, Orwell and Roach rivers in Essex, south-east England. The Blackwater is a similar muddy estuary located between the Orwell and Roach. Jeffreys wrote, “I propose it as a distinct species with some misgiving; for, although I have not yet seen any intermediate form, it has not been ascertained that the two live together, and the present form seems to be peculiar to brackish water and mud.” In September 2019, S. T. collected a sample of 220 shells from the Blackwater. His find almost replicated Jeffreys’ experience as all accorded with his description, with the exception of a single typical T. reticulata (Linnaeus, 1758), shown in fig. 1, which stood out as paler, having almost flat whorls, and being larger than all but four of the others (Jeffreys stated that those he found were smaller than T. reticulata). The exception diminishes Jeffreys’ misgiving about the two species not living together as it was in good condition, suggesting it had not been transported far and probably lived near the T. nitida.

Sympatric populations of the two species living in the Ria de Vigo, Spain, have been described in detail by Rolan and Luque (1994). Some of the differentiating features that they listed, and which are visible in fig.1, are listed above and have been labelled by odd numbers for T. nitida and even numbers for T. reticulata.

The World Register of Marine Species (WoRMS) accepts T. nitida as a valid species, supported by chromotology (Collyer, 1961), comparative morphology (Rolan & Luque, 1994), allozymes (Sanjuan et al., 1997) and DNA (Couceiro et al., 2012). There is widespread recognition of it by recorders in continental Europe and continental identification guides such as Trigo et al. (2018) but, strangely for a species first described by an Englishman with English specimens, virtually no recognition of it by recorders in Britain and Ireland. In 1895 in the Journal of Conchology, Marshall wrote;

“This is so obviously a variety of N. reticulata, that it has been tacitly ignored as a species as published in [Jeffreys, 1867] British Conchology. - - - the number of ribs [costae] in the type [N. reticulata] are exceedingly variable, being nearly twice as many in some specimens as in others.”

The numbers of costae vary within each species, and an overlap occurs between the species in southern Europe, but other morphological features and DNA separate them. No overlap in number of costae on the body whorl of non-juveniles was found in a comparison of T. nitida (10 to 14) from Essex with T. reticulata (15 to 23) from widespread sites in Britain (I.F.S. pers. obs.).

Marshall’s opinion has held sway in Britain and Ireland through Chaster et al. (1901), McClelland (1926), Winckworth (1932), and Turk (1973). Some publications mention it as a variety of T. reticulata. McMillan (1968), Fretter and Graham (1985) and Graham (1988) mention the possibility that it might be a separate species, but deal with it within the description of T. reticulata.

At the time of writing, NBN Atlas does not have a U.K. distribution map for T. nitida, but the UK Species Inventory, on which the NBN Atlas Species Dictionary is based, is to be altered to encapsulate the current concept of T. reticulata into a sensu lato concept for all the pre-split records and to create the two new concepts of T. reticulata sensu stricto (Linnaeus, 1758) and T. nitida (Jeffreys, 1867), (C. Raper, [the Natural History Museum] 2019, pers.comm. 27th September). There are no on-line available records of it in Ireland, but its distinctive egg capsules, in the proximity of adults, have been photographed in County Galway at Aughrus Pier and Killary Fjord (fig. 2 flic.kr/p/2hqPSy3 ). T. nitida egg capsules have also been photographed in the Oosterschelde (fig. 3 flic.kr/p/2hqSEns ) on the Dutch coast facing the Essex coast. All these sites are sheltered waters, like the Essex estuaries and Ria de Vigo.

The lack of recognition of T. nitida in Britain and Ireland has probably been perpetuated by the species account of T. reticulata [as Hinia reticulata] in Graham (1988), which is widely regarded as the standard British identification guide for shelled marine gastropods. T. reticulata is also described at greater length in its forerunner, Fretter and Graham, (1985). In both books, the same two specimens are illustrated. One from Harwich near the mouth of the Orwell Estuary, the type locality of T. nitida, captioned Hinia reticulata var. nitida is obviously T. nitida, though the lack of columellar or parietal tubercles often found on T. reticulata and absent from T. nitida is explained away by saying it is not fully mature, despite being 24mm high and near the maximum height of T. nitida from Essex. The other specimen illustrated, though not labelled var. nitida, is also T. nitida with convex whorls, no tubercles/teeth within either outer or inner lips and coming from Hellebaek on the low and variably saline Øresund, suited to the tolerant T. nitida. Egg capsules with the shape of those of T. nitida, drawn by G. Thorson who studied the marine invertebrates in the Øresund, are illustrated and labelled T. reticulata in Yonge and Thompson (1976).

Users of Graham (1988) with a specimen of T. nitida to identify will have found a close fit with the images purporting to be T. reticulata and almost certainly recorded it as such. Conversely, many, including I.F.S. will have been puzzled by the poor match of the illustrations when identifying typical flat-whorled T. reticulata specimens.

With the help of several contributors, an illustrated account is being created which will compare the two species in more detail. In the meantime, we hope this will raise awareness of the situation and prompt close examination of Tritia specimens, especially from sheltered waters such as the rias of south-west England. We have many specimens of beached T. nitida shells, but the colours are faded and most are partially eroded. We would be very grateful to receive recently live-collected T. nitida shells from Britain or Ireland for photography for the account. (We have generous contributions of live-collected shell images in standard postures from the Adriatic.)

Acknowledgements

We are most grateful to Mark Thomas and Bas van der Sanden for use of their images in this article.

Links and references

Chaster, G.W.; Knight, G.A.F.; Melvill, J.C. and Hoyle, W.E. 1901. List of British marine mollusca and brachiopoda. Manchester, Conchological Society of Great Britain and Ireland.

Collyer, D.M. 1961. Differences revealed by paper partition chromatography between the gastropod Nassarius reticulatus (L.) and specimens believed to be N. nitida (Jeffreys). J. Mar. Biol. Ass. 41(3): 683 to 693.

Couceiro, L., López, L., Sotka, E.E., Ruiz, J.M. & Barreiro, R. 2012. Molecular data delineate cryptic Nassarius species and characterize spatial genetic structure of N. nitidus. J. Mar. Biol. Ass. 92(5): 1175 to 1182.

Fretter, V. and Graham, A. 1985. The prosobranch molluscs of Britain and Denmark. Part 8 – Neogastropoda. Suppl. 15, J. Moll. Stud.

Graham, A. 1988. Molluscs: prosobranch and pyramidellid gastropods. Synopses of the British Fauna (New Series) no.2 (Second edition). Leiden, E.J.Brill/Dr. W. Backhuys. 662 pages.

Jeffreys, J.G. 1862-69. British conchology. vol. 4 (1867). London, van Voorst. (As Nassa reticulata) p346 in pdf archive.org/stream/britishconcholog04jeffr#page/346/mode/2up .

Original description of T. nitida (as Nassa nitida) on p349 at archive.org/stream/britishconcholog04jeffr#page/348/mode/2up

Marshall, J. T. 1895. Alterations in ‘British Conchology’. J. Conch. 8: 24 to 41.

www.biodiversitylibrary.org/item/99811#page/60/mode/1up [p38 as Nassa nitida]

McClelland, H. 1926. General index of all families, genera, species and varieties described and noted in the Journal of Conchology vols. I – XVI, 1874 to 1922. Proceedings of the Malacological Society of London vols. I – XV, 1893 to 1923. The Conchologist vols I – II, 1891 to 1893, continued as the Journal of Malacology vols. III – XII, 1894 to 1905. Birmingham, Birbeck and sons.

McMillan, N.F. 1968. British shells. London, F. Warn.

Rolan, E. and Luque, A.A. 1994. Nassarius reticulatus (Linnaeus, 1758) and Nassarius nitidus (Jeffreys, 1867) (Gastropoda, Nassariidae), dos especies válidas de los mares de

Europa. Iberus, 12 (2): 59-76.

www.biodiversitylibrary.org/page/32628640#page/153/mode/1up

Sanjuan, A., Pérez-Losada, M. & Rolan, E. 1997. Allozyme evidence for cryptic speciation in sympatric populations of Nassarius spp. (Mollusca: Gastropoda). J. Mar. Biol. Ass. 77(3): 773 to 784.

Thorson, G. 1946. Reproduction and larval development of Danish marine bottom invertebrates; with special reference to the planktonic larvae in the Sound (Øresund). Meddelelser fra Kommissionen for Danmarks Fiskeri- og Havundersøgelser. Serie Plankton. 4 (1): 1–523.

Trigo, J.E.; Diaz Agras, G.J.; Garcia Alvarez, O.L.; Guerra, A.; Moreira, J.; Pérez, J.; Rolán, E.; Troncoso, J.S,; Urgorri, V.. 2018. Guia de los Moluscos Marinos de Galicia. Servicio de Publicacións da Universidade de Vigo.

Yonge, C.M. and Thompson, T.E. 1976. Living marine molluscs. Collins, London. [Fig. 52G shows Danish egg capsules of T. nitida labelled as Nassarius reticulatus.]

Current taxonomy: World Register of Marine Species (WoRMS) www.marinespecies.org/aphia.php?p=taxdetails&id=890057

Stella convessa - Convex star. by Francesco Guarnieri

10 4

Modular origami, no cuts, no glue, 5 squares of copy paper, 10,5 x 10,5 cm.

Designed and folded by Francesco Guarnieri, May 2017.

In 2017 the diagrams were published in the booklet of the Centro Diffusione Origami, QQM 60, Poesie e geometrie di carta:

flic.kr/s/aHsksy219M

In 2018 the diagrams were published in the journal of the Asociación Española de Papiroflexia, Pajarita n° 144

Other information: guarnieri-origami.blogspot.it/2017/05/stella-convessa-con...

Colwich-Convex-Capers. by 'Mikey' Hurley

10 8

The already elusive Boston steel, became a little bit more so today by not running, which meant that I moved on from Burton, to my second location; Colwich.

I spent some time at the lock photographing Pendolinos and a variety of Sheds in different clothing and also much to my enjoyment, a narrow boat which drifted into the lock and out some five minutes later and a few feet lower. Whilst waiting for trains, the owner of the lock house came out, made me a steaming cup of coffee and gave me a chocolate bar too. There really are some fantastic people out there!

1A47. Colwich. 19-3-16

Convex mirror selfie by Ambulant

1 1

Emerging from the pedestrian underpass next to Fullers Brewery in Chiswick

Bubble Time by Western Maryland Photography

15 18

Mine and Nikola's convex reflection in a soap bubble

Concave and Convex Buddles, Poldice Mine by Roger Powley

11 4

Pairs of convex and concave buddles were used to separate the tin or copper grains of ore from the waste material (gangue). The wooden frameworks which held the rotating brushes have long since rotted away, leaving just the concrete bases.

convex goodness by golfpunkgirl

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Convex or Concave? Tiffany Glass <3 by northern star pics

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This building was almost torn down

Chicago Cultural Center, saved from the wrecking ball by Sis Daley, wife of Da Mayor. Amazing mind blowing beauty and art. To add to the atmosphere, the building was filled with live classical music. That dome is Tiffany glass btw, more photos to follow....

Completed in 1897 as Chicago’s first central public library, the building was designed to impress and to prove that Chicago had grown into a sophisticated metropolis. The country’s top architects and craftsmen used the most sumptuous materials, such as rare imported marbles, polished brass, fine hardwoods, and mosaics of Favrile glass, mother-of-pearl and colored stone, to create an architectural showplace. Located on the south side of the building, the world’s largest stained glass Tiffany dome ― 38 feet in diameter with some 30,000 pieces of glass ― was restored to its original splendor in 2008. On the north side of the building is a 40-foot-diameter dome with some 50,000 pieces of glass in an intricate Renaissance pattern, designed by Healy & Millet... from the Cultural Center web site.

Concave/Convex by AntyDiluvian

5

Taken in 2005.

Two wings of the Intercontinental Boston on Atlantic Avenue, one concave (on the left, luxury condos) and one convex (on the right, luxury hotel).

colourful globe by antschy

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www.youtube.com/watch?v=i7m1gCdHi0s

Convex reflection by JW.Andrews

6

A reflection in a bauble that didnt make its way into storage

Convex Canyon by Woody Wade

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Another canyon of the San Juan River, SE Utah, a bit lower (i.e. east) of the other pictures here.

binged.it/1VExin9

Reflected Convexly by Jeff Stewart

5

Project 365 = Day 61 = 2 Mar 2025

Day 1157 (Since 1 Jan 2022)

03 Patella ulyssiponensis. Length 40mm. North Yorkshire. September 2014. by Morddyn

1

Highest profile (H/L 34%) in sample of eighteen.

In profile, anterior and posterior slightly convex.

SPECIES DESCRIPTION part B BELOW

SPECIES DESCRIPTION part A flic.kr/p/BG8mKq

Key id. features 4Pu flic.kr/p/BG8hhs

OTHER SPECIES ALBUMS www.flickr.com/photos/56388191@N08/collections/

GLOSSARY below.

Patella_ulyssiponensis Gmelin, 1791

Identification of British patellid limpets.

With the exception of shells with height >50% of length (only P. vulgata grows that high, but many P. vulgata have low shells), shell-exteriors cannot be relied on, and shell-interiors can be confusing. Examination, in good light under magnification, of extended pallial tentacles on living animals is essential for consistent accurate discrimination of the three rock-dwelling Patella species. Best achieved with specimen adhering to underside of supported glass-sheet in black-based container of seawater.

Some morphologically intermediate forms can only be reliably identified by sequencing DNA or allozyme study. Intermediates result from similar environmental factors affecting different species in similar ways and are not hybrids (Sanna et al., 2011 and Sá-Pinto et al., 2007). For the purpose of recording for distribution schemes it is advisable to disregard intermediates unless DNA or allozymes can be employed, especially beyond or on the limits of known distributions. Intermediates most frequent near limit of distributions of P. depressa and P. ulyssiponensis in Isle of Wight , perhaps because conditions not optimal (Fretter and Graham, 1994).

Key identification features of typical British specimens.

Patella ulyssiponensis

1. Basal half of pallial tentacles has opaque pigment which can be white, off-white, cream or, on large specimens, yellowish or orange. The distal half fades to a translucent tip. Opaque basal half is often distinct from translucent mantle-skirt that they arise from, so it is possible to confuse with P. depressa. It is important to use pallial tentacles in combination with foot-colour/shell-length for identification. Examples at 26Pu flic.kr/p/BGqszN .

2. Foot that is NOT pitch-brown/black or dark khaki. It can be whitish when young 30Pu flic.kr/p/BGqk4q becoming yellowish 31Pu flic.kr/p/BGrKw1 and, sometimes, orange with age 21Pu flic.kr/p/AUuNww . Juveniles under 12mm length may show a blackish internal shadow through the thin pale translucent foot 30Pu flic.kr/p/BGqk4q as they lack gonads above the foot that mask the dark viscera in adults.

Similar species

Patella vulgata

Extremely variable species; foot colours and nearly all shell-features have overlaps with P. depressa and P. ulyssiponensis.

1. Pigment-less pallial tentacles are slender, translucent and same colour as mantle-skirt they arise from. 40Pu flic.kr/p/BPJ1vQ .

Cautions:

Pallial tentacles of P. vulgata may look white when arise from colourless mantle-skirt in some lighting, but no pigment 41Pu flic.kr/p/AUxuXs .

Translucency and fineness of pallial tentacles of P. vulgata often make discernment difficult, especially when mantle skirt retracted from shell-rim and pallial tentacles viewed against shell 42Pu flic.kr/p/BGtg3y ; often virtually invisible when out of water as may be retracted as well as highly translucent 43Pu flic.kr/p/AUDqUz .

Foot colour of P. vulgata varies greatly, sometimes orange resembling P. ulyssiponensis 53Pu flic.kr/p/BPKsw5.

Shell interior can be white or tinted orange in P. vulgata 53Pu flic.kr/p/BPKsw5 and 44Pu flic.kr/p/BPKJ6G .

Patella depressa

[1 & 2 in combination, not singly, are diagnostic of typical specimens but exclude intermediates.]

1. Pigmented pallial tentacles are opaque chalky-white for more than half of extended-length; may have translucent tip; distinctly whiter than buff mantle-skirt from which they arise 45Pu flic.kr/p/BJLMBx . Even when mantle-skirt retracted, pallial tentacles often clearly visible contrasting with the darker mantle 46Pu flic.kr/p/AUxm6u .

2. Sole of foot pitch-brown 47Pu flic.kr/p/AUDiJH to black 46Pu flic.kr/p/AUxm6u .

3. On shell-interior, whitish projecting points of ribs have short, unglazed, chalky, pure-white central line, but reduced or lacking where projecting points of ribs eroded 48Pu flic.kr/p/BS4e7v . [This feature recently recognised by S. Payne, and applies to all in large sample examined by IFS. Unsure yet if universal on P. depressa and exclusive of P. vulgata and P. ulyssiponensis.]

Caution:

Shell interior can be orange-cream in P. depressa 49Pu flic.kr/p/BixiVz

Patella caerulea Linnaeus, 1758.

Does not occur in Britain. In Iberia and Mediterranean, separation from it of some specimens of P. ulyssiponensis could not be achieved with foot colour and shell morphology by Sanna et al. (2011) who relied on the use of DNA sequencing. They did not mention attempting the use of pallial tentacle colour on live specimens; it may be worth investigation. See Sanna et al. for images of P. caerulea.

Habits and ecology

P. ulyssiponensis is a southern species which reaches its northern limit in south-west Norway and locally at cold winter-sea areas of Baltic, North Sea and north-east Irish Sea. It lives on rocky shores with Ballantine (1961) wave exposure scale 1- 4 or 5 where turbidity does not prevent algal growth. It is often the dominant species of limpet at mid- and low-tide levels on extremely and very exposed shores (scales 1 & 2). It can be common on exposed (scale 3) lower shores, and present on semi-exposed shores (scale 4) but largely confined to lower levels or to pools lined with encrusting calcareous algae at higher shore levels. On fairly sheltered (scale 5) shores it is absent or confined to pools. It is usually found on bedrock, not on shingle or loose boulders, and it extends into the sublittoral zone. It is unable to produce very large, thick, high-domed shells, like those of some P. vulgata 50Pu flic.kr/p/AUDcK8 , to resist desiccation on drained rock on upper shores. P. ulyssiponensis is reported to be a consistently homing species (Branch, 1981a); adults always after feeding-excursions seeking to return to same position where a deep home-scar can be developed when substrate is relatively soft encrusting calcareous algae 7Pu flic.kr/p/AUibCP . Differences in amount of opaque, white, porcelaneous material on interior of shells at different localities may be due differences in suitability of environment 15Pu flic.kr/p/AUm6kt . Locomotion by retrograde waves alternating on each side (ditaxic) of sole; muscles alternately compress/relax against blood trapped between them to create waves. Feeding: most frequently grazes on calcareous encrusting algae and Corallina, ingesting the algae and organic deposits on their surface. Grazing is facilitated by powerful muscles in large buccal mass, and by rust-coloured iron-reinforced teeth on long radula with plentiful replacements for worn teeth 36Pu flic.kr/p/AUvMhW . Length varies seasonally; shorter when wear of active feeding exceeds growth rate. Patella spp. wear out up to two rows of teeth per day (Sigel, 2008 ). About four rows of teeth are in contact with substrate during feeding; loose particles are retained by rim of surrounding jaw# and the licker 38Pu flic.kr/p/BJKboP which sweeps them up at the end of the radula stroke. Long coiled intestine compacts faeces (often yellowish from high lime content obtained from calcareous algae) 35Pu flic.kr/p/BivTv4 into firm faecal strings that will not contaminate gills in pallial groove; compensates for adults lacking hypobranchial gland to produce mucus to bind particles exiting from nuchal cavity. Cilia on roof of nuchal cavity and side of foot conduct faecal matter from anus in nuchal cavity to middle of right side 24Pu flic.kr/p/BS1DhR . Faeces and debris accumulate there until periodic sharp contraction of pedal-retractor muscle clamps shell down and forcefully flushes water and waste out of shell (Fretter & Graham 1962 & 1994). When limpets removed from rock, accumulated pile of faecal strings often found in position. Cilia also create inhalent water-current from left of head through nuchal cavity, where urogenital openings located, and thence carry excreta and ova/sperm to exterior. Colourless interior shell-layers may be stained orange by digestive gland when feeding on red algae in both P. ulyssiponensis 4Pu flic.kr/p/BG8hhs and P. vulgata 43Pu flic.kr/p/AUDqUz Predators reported to be able to dislodge P. vulgata shells probably take P. ulyssiponensis too; they include gulls (Larus spp.), oystercatchers (Haematopus ostralegus), crabs, starfish and rats. Nucella lapillus bores through the shell, usually to the pedal-retractor muscle where the adjacent viscera are accessible obliquely to its radula without having to bore through the thick amphora# shell-layers covering the viscera 51Pu flic.kr/p/AUDb42 . Boring takes several days, but is rewarded with a large food supply, providing the Nucella isn't dislodged before completion . Respiration: gill-cilia create gentle local inhalent respiratory water currents all around perimeter of animal from adjacent shell-rim onto gills, and exhalent currents below gills back to shell-rim 24Pu flic.kr/p/BS1DhR (Yonge & Thompson, 1976). Densely ciliated groove on stalk and rim of each gill-lamella catches and removes large particles of detritus that would clog gill (Fretter & Graham, 1994) 25Pu flic.kr/p/BGqt5A . Blood passes from viscera and foot via vessels through gaps in encircling pedal-retractor muscle 23Pu flic.kr/p/BGqwhs into gills for oxygenation, and thence into encircling efferent pallial vessel in mantle-skirt, which carries blood to left of nuchal cavity and through its roof to elongated heart behind left of cavity 52Pu flic.kr/p/BpVk1S for recirculation to head, foot and viscera (Fretter & Graham, 1994). On shells with thick porcellaneous interior layers, efferent pallial-vessel leaves a mark where it passes through gap in gills to enter nuchal cavity 1Pu flic.kr/p/BpzHx5 & 14Pu flic.kr/p/BpCkES . Breeding season varies geographically; June-September N.E. England, June-November S.W. England, and precise timing varies year to year (Fretter & Graham, 1994). External fertilization, so close proximity of sexes required for success. Sperm and ova shed into water column, ova individually. Eggs hatch as free trochophore larvae (stage passed within egg by most “less-primitive” spp.) in plankton before transforming to veligers and, after a short planktonic-life, settling on lower shore and assuming limpet form. Spat, when 1mm long, have eight radiating ridges; P. vulgata has five ridges on right, four on left. P. depressa has ten (Fretter & Graham, 1994). Some move to mid-tide level when shell-length 5mm.

Distribution and status

Mediterranean, Black Sea and North-east Atlantic from Morocco to Shetland and Bergen, Norway (Høisæter, 2009). Not in the colder waters of a) the Baltic b) North Sea from Stavanger to Le Havre and from Flamborough to Beachy Head c) north-east of Irish Sea from Kircudbright or Dumfries to Anglesey.

GBIF map www.gbif.org/species/5190390 ; Belgian and Dutch records are from flotsam (Fretter & Graham, 1994, p.464) and records on Macaronesian islands are misidentified P. aspera Röding, 1798 (“note” at www.marinespecies.org/aphia.php?p=taxdetails&id=456570)

U.K. distribution map NBN species.nbnatlas.org/species/NHMSYS0021056398

Acknowledgements

I gratefully acknowledge Dr Sebastian Payne for information, discussion and help during shore-work. Any errors or omissions are the responsibility of the author.

Links and references

Akşit, D. & Falakil Mutaf, B. 2011. The external morphology of the gill of Patella caerulea L. (Mollusca: Gastropoda). Turk. J. Zool. 35(4) 603-606. Tübitak. Turkey. PDF contains SEM images of gill.

www.google.co.uk/search?q=patella+gill+ciliated+groove&am...

Backeljau, T. 1986. Lijst van de recente mariene mollusken van Belgie Koninklijk Belgisch Instituut voor Natuurwetenschappen, Brussels.

PDF at www.marinespecies.org/imis.php?module=ref&refid=4414

Barber, A.H., Lu, D. & Pugno, N.M. 2015 Extreme strength observed in limpet teeth The Royal Society.

rsif.royalsocietypublishing.org/content/12/105/20141326

Branch, G.M. 1981a. The biology of limpets. Oceangr. Mar. Biol. Ann. Rev. learning.watfordboys.org/mod/resource/view.php?id=4730

Branch, G.M. 1981b. The biology of limpets. Oceangr. Mar. Biol. Ann. Rev. www.google.co.uk/search?q=Patella+vulgata+blood+circulati...

Cohen, A.L. & Branch, G.M. 1992. Environmentally controlled variation in the structure and mineralogy of Patella granularis shells from the coast of southern Africa: implications for palaeotemperature assessments. Palaeogeography, palaeoclimatology, palaeoecology, 91: 49-57. www.whoi.edu/fileserver.do?id=163844&pt=2&p=36767

Forbes, E. & Hanley S. 1849-53. A history of the British mollusca and their shells. vol. 2 (1849), London, van Voorst. (As Patella athletica; PDF at archive.org/stream/historyofbritish02forb#page/424/mode/2up Use slide at base of page to select pp.425-429.)

Fretter, V. and Graham, A. 1962. British prosobranch molluscs. London, Ray Society.

Fretter, V. and Graham, A. 1994. British prosobranch molluscs. Revised and updated edition. London, Ray Society.

Gmelin, J.F. (1791) Vermes. In Gmelin J.F. (Ed.) Caroli a Linnaei Systema Naturae per Regna Tria Naturae, Editio Decima Tertia, Aucta Reformata. Tome 1, Pars 6 (Vermes). G.E. Beer, Lipsiae [Leipzig], pp. 3021-3910., available online at www.biodiversitylibrary.org/item/83098#5 Original description on p.692 of PDF .

Goshima, S., Ilano, A.S., Ito, A. & Nakao, S. 2002. Seasonal and tidal-height variations in body weight and radular length in Nodilittorina radiata (Eydoux & Souleyet, 1852). J. Mollus. Stud. 68: 197-203.

PDF at mollus.oxfordjournals.org/content/68/3/197.full.pdf+html

Graham, A. 1988. Prosobranch and pyramidellid gastropods. London.

Høisæter, T. 2009. Distribution of marine, benthic, shell bearing gastropods along the Norwegian coast. Fauna Norvegica 28: 5-106.

pdf at www.ntnu.no/ojs/index.php/fauna_norvegica/article/view/563

Jeffreys, J.G. 1862-69. British conchology. vol. 3 (1865). London, van Voorst. (As Patella vulgata var. 4 depressa, incorrectly attributed to Pennant.); Free PDF at archive.org/stream/britishconcholog03jeff#page/236/mode/2up . Use slide at base of page to select pp.237.

MacClintock, C. 1967. Shell structure of patelloid and bellerophontid gastropods (Mollusca). Peabody Museum of Natural History, Yale University. Bulletin 22. pdf at

www.google.co.uk/?gws_rd=ssl#q=MacClintock%2C+C.+1967.+Sh....

215 pages, may take a few minutes to download. Contents on page v.(= p.6 of pdf). To find pages on pdf add 1 to Roman numerals, and add 11 to modern numerals.

Pennant, T. (1777). British Zoology, vol. IV. Crustacea. Mollusca. Testacea. London. i-viii, 1-154, pls. 1-93.,

Page 142 biodiversitylibrary.org/item/127011#page/168/mode/1up

Pl. 89 fig.146. biodiversitylibrary.org/item/127011#page/361/mode/1up

Sanna, D., Dedola, G. L., Lai, T., Curini-Galletti, M. & Casu, M. 2011. PCR-RFLP: A practical method for the identification of specimens of Patella ulyssiponensis s.l. (Gastropoda: Patellidae), Italian Journal of Zoology,

pdf at www.researchgate.net/publication/233126771_PCR-RFLP_A_pra...

Sá-Pinto, A., Branco,M., Harris, D.J. & Alexandrino, P. 2005. Phylogeny and phylogeography of the genus Patella based on mitochondrial DNA sequence data. J. Exp. Mar. Biol. Ecol. 325: 95-110.

Sá-Pinto, A., Alexandrino, P. & Branco,M. 2007. High genetic differentiation with no evidence of hybridization between four limpet species (Patella spp.) revealed by allozyme loci. Scientia Marina 71(4): 801-810. Barcelona. pdf at www.vliz.be/imisdocs/publications/131981.pdf

Yonge, C.M. and Thompson, T.E. 1976. Living marine molluscs. London.

Current taxonomy: World Register of Marine Species (WoRMS)

www.marinespecies.org/aphia.php?p=taxdetails&id=140684

GLOSSARY

amphora – (on interior of limpet shell) Roman amphora-shaped area enclosed by scars of pedal-retractor muscle and anterior mantle-attachment.

anteroposterior – (of linear feature) aligned from anterior to posterior.

aperture – mouth of gastropod shell; outlet for head and foot.

apex - earliest formed part of a gastropod shell, the summit of the cone. (In this limpet-account restricted to the exterior of the shell, and “vertex” used for the interior.)

auct. - (abbreviation of “auctorum” = “of authors”) name, often of another valid species, used in error for this one by other author(s). en.wikipedia.org/wiki/Auctorum

cephalic – (adj.) of or on the head.

cilia – (pl.) microscopic linear extensions of membrane that move in rhythmic waves to create locomotion, or move particles and liquids e.g. inhalent water currents. (“cilium” singular). (Electron scanning microscope image at flic.kr/p/qQB5zj )

ciliary – (adj.) relating to or involving cilia.

coll. – in the collection of (named person or institution) (compare with legit).

conoid – shaped like a cone.

ctenidium – comb-like molluscan gill; usually an axis with a row of filaments either side.

ELWS – extreme low water spring tide (usually near March and September equinoxes).