360 SHELLS AND SHELL-FISH. PART II. 



any spire ; the base widest : this in the typical species, 

 is covered by the lobes of the mantle; in others the 

 whole animal is contained in the shell.* 



Lam. Shell internal, oval, colourless ; inner 

 lip thin ; apex umbilicated ; animal oblong, without 

 tentacula. 

 aperta. Sow. Man. f. 248. ? Guildingii Sw. (See^. 46.) 



Sulla. Animal furnished with two connected bony 

 plates ; shell obovate ; contracted above, and effuse 

 at the base. 



B. Lignaria. Sow. Man,, f. 251. 



Vesica Sw. Animal unknown ? probably contained 

 within the shell ; shell oval, solid ; apex umbi- 

 licated ; aperture entire ; contracted above. 

 ampulla. Sow. Man. f. 252. Naucum. Sow. Man. f. 250. 



Aplustra Schum. Animal - ? shell solid, but thin ; 

 furnished with a distinct but depressed spire. 

 A. fasciata. Sow. Man. f. 249. 



Bullinula Beck. General shape of the last ; but the 

 spire is slightly produced and conic : a doubtful 

 type ? 



B. lineata. Sow. Man. f. 253. 



Vitrella Sw. Animal - ? shell internal, hyaline, 

 or sub-transparent ; convolute ; the apex carinated ; 

 the substance elastic. 



V. fragilis. Sow. Man. f. 247. 



DOBIDIUM Mecken. Animal with the lobes dilated into 

 fin-like processes, but without a shell. 

 D. carnosa. Cuv. Mem. 



SUB-FAM. 4. GASTEROPTERID./E. 

 GASTEBOPTERON Meek. Animal short, ovate, natatorial ; 

 the margins of the foot dilated into broad wing-like 



* The arrangement of this sub-family, founded chiefly upon the shell, 

 is purely artificial, no knowledge having been gained of the greater part of 

 the animals. Such genera as Cryptella, &c., founded merely upon the 

 branchial covering of some unknown animal, can never be admitted into 

 Malacology. 



