Velutinids are prosobranch gastropods of the  family Velutinidae (sometimes referred to as the family Lamellariidae). They have a fully internal shell that is covered by the mantle which is often elaborately colored or ornamented. They are frequently mistaken for dorid nudibranchs. They may be distinguished by their cephalic tentacles that emerge from beneath the mantle and by the bulbous eye spots at the bases of those tentacles. They feed on colonial tunicates. A few of the species most frequently mistaken for sea slugs:

Lamellaria sp. #2 CP: Airport Beach, Maui; Aug. 7, 2002	Marsenina(?) sp. #1 CP: Kahului Harbor, Maui;  April 8, 2010	Marseniopsis sp. #1 CP: Maalaea Bay, Maui; Oct. 22, 2007
Marseniopsis sp. #2 CP: Napili Bay, Maui;  Sept. 12, 1998	Lamellaria sp #1 CP: Kapalua Bay, Maui; April 17, 2009	Coriocella nigra CP: Kapalua Bay, Maui; May 22,  2008

For more information see: The velutinid addendum on this site   Velutinids on the Sea Slug Forum   Okinawan velutinids by Robert Bolland   Velutinids on Nudipixel