Velvialucent clouds (MF Pentax 645Nii / Velvia 100)

Taken from Fiordland Lodge Te Anau, looking across Lake Te Anau, South Island, New Zealand at sunset.

 

'L' or left-click to zoom.

 

Pentax 645Nii, Pentax SMC 35mm F/3.5, Velvia 100

 

Nikon Supercoolscan 9000ED

Straight from the scanner.

 

I am not a cloudologist (?!) so I will defer my analysis to those more expert at cloud identification than I. Please can you help me ... What is this cloud?

Done