BULUD^E. 409 



has the precedence. Our shell varies in thinness,, in 

 comparative length and breadth, and in the turgidity of 

 the body-whorl. 0. carnea is not uncommon in the 

 Mediterranean; the young is probably Risso's Simnia 

 nicceensis. 



Order IV. PLEUEOBRANCHIATA, Gray. 

 (See Vol. III. p. 200.) 



In the same year that Dr. Gray proposed the name 

 which I have adopted for this order, Professor Loven pub- 

 lished another name, viz. Pomatobranchia. I now place 

 it immediately after the Siphonobranchiata, and post- 

 pone the Pulmonobranchiata (as being more perfect 

 Gastropods) not only to the present order, but also to 

 the Nudibranchiata and Pellibranchiata. I accidentally 

 omitted in page 265 " Order III. SIPHONOBRAN- 

 C HI ATA." The families Cerithiopsida to Cyprmda 

 inclusive belong to the last-named order ; and the num- 

 bers prefixed to them (viz. XXVI. to XXXI.) ought 

 therefore to be I. to VI. 



Family I. BUL'LIME, (Bulladce) Clark. 



BODY gelatinous, generally divided into separate parts or 

 lobes, and not always containable within the shell : head 

 snout-shaped : tentacles either united and forming a hood or 

 head- veil, or consisting of two distinct and broad lappets : 

 eyes, when present, sessile or subcutaneous, at the base of the 

 tentacles or at the sides of the head : foot usually large, some- 

 times expanded on each side, like fins (epipodia) which serve 

 for swimming, as well as behind into a single lobe (meta- 

 podium), so as to cover the crown or apex of the shell : gills 

 forming a single triangular plume, which is placed across the 

 back on the right side, and protected by the shell : gizzard 

 peculiar to most (if not all) genera, and composed of several 



VOL. IV. T 



