Costasiella sp. 4 is C. usagi

Thanks Clay & Patty-Jo,
I'm afraid I looked at Ichikawa's paper but after looking at her illustration of this species, which shows totally black rhinophores and no sign of longitudinal lines, I didn't dwell on her description. Species of Costasiella obviously show considerable colour variation which makes our interpretation of Ichikawa's descriptions quite difficult since they are often based on very few animals. Until we have a better understanding of intraspecific variability it is going to be difficult to identify her species.

Costasiella usagi is a good example. In Ichikawa's description the colour is described as:
"The head and tail are not pigmented,, and the rhinophores are black. The median cerata are grey, while the outer ones are black. All the cerata possess a white end and a black tip. Moreover, all the cerata bearl longitudinal striations reaching from the base of each ceras to the white apical portion. ... The ventral side of the foot is white. .... Smaller specimens have the median cerata coloured green, instead of grey."

Ichikawa doesn't say what colour the longitudinal striations are. I am happy to accept you view that they are white, and if you look carefully at Nil's photo a few of the larger anterior cerata seem to have some black pigmentation. This is certainly a good example of the dangers of describing new species prematurely. If you have photos of this species showing colour variants they would be a welcome addition.
Best wishes
Bill Rudman