MA1ACOZOA. GASTEROPODA. PECTINIBRANCHIATA. 161 



Not uncommon off the coast, in deep water. 



This shell having heen erroneously referred to Helix laevi- 

 gata of Linnaeus, characterized as "laevissima" and " magni- 

 tudine pisi," I offer no apology for giving it a specific name 

 consistent with truth. 



The impropriety of converting specific into generic names 

 is very apparent in this genus, in which Velutina is applicable 

 to one of the species only. 



Helix laevigata. Mont. Test. Brit. 382. Velutina laevigata. 

 Flem. Brit. Anhn. 326. Velutina laevigata. Johnst. B. Tr. iii. 

 275. / 



GENUS 2. CORIOCELLA. 



Animal with the body elliptical, much depressed, hav- 

 ing the borders of the mantle very thin, notched in front, 

 and spreading out widely all round ; the foot oval, very 

 small ; the head scarcely distinct ; two tentacula con- 

 cealed under the shield, rather thick, short, contractile ; 

 the eyes at the base of the tentacula externally. 



Shell extremely thin, membranous in part, concealed 

 in the mantle, ear-shaped, with a small spiral turn at 

 the apex. 



1 . Coriocella flexilis. Flexible Coriocella. 



Shell ear-shaped, membranous, flexile ; being formed of a 

 layer of epidermic substance, transversely lamelloso-striate, 

 and of a pale olivaceous colour, with an extremely thin glossy 

 opaque, white layer of calcareous matter, along the inner lip 

 and spire. It may further be described as oval-oblong, with the 

 aperture extremely large and oval, the inner lip thin but 

 obtuse, the outer very thin and edged, the apex convoluted 

 into a single turn, the upper surface convex, the interior glossy. 

 Length half an inch, breadth four-and-a-half twelfths. 



A shell, without the animal, found by me, at Aberdeen, in 

 the Winter of 1841 ; another, by Mr. Alexander Murray, on 

 the Buchan coast, in September, 1842. 



Bulla flexilis. Laskey, Wern. Mem. i. 396. PL 8. f. 6. Bulla 

 flexilis. Mont. Test. Brit. Suppl. 1 68. Sigaretus flexilis. Brown, 

 Illustr. PL 44. f. 3, 4. Bulla flexilis. Flem. Brit. Anim. 294. 



o 2 



