18 



GASTEROPODA. 



In the genus Ncrincea (figs. 399 and 400) the shell is 

 turreted, niany-whorled, and nearly cylindrical. The colum- 

 ella carries continuous ridges, and similar ridges exist on the 



Fig. 39S.— Ceri«t«(TO 

 hexagonitm. Eocene 

 Tertiary. 



..:^JM 



Fig. 399. — Neriricea 

 hisulmta. Clialk. 



Fig. iOO.—Nerincea Goodhallii, 

 one-fom-thofthe natural size. The 

 left-band figure shows tlie appear- 

 ance presented by the sliell when 

 vertically divided. Coral Rag, 

 England. 



interior of the whorls, so that casts of the interior of the 

 shell are often very unlike the form of the exterior. The 

 aperture of the shell is channelled 

 in front. The species of JVerincea 

 are exclusively Jurassic and Creta- 

 ceous, and are very numerous. One 

 of the limestones of the Jura, be- 

 lieved to be of the age of the Coral 

 Eag (Middle Oolite) of Britain, 

 abounds to such an extent in these 

 shells as to have gained the name 

 of " Calcaire a Neriuees." 



With the preceding may be as- 

 sociated the Secondary genera Mi- 

 st oma, Exclissa, Fibula, Crypto'ploeus, 

 and Ceritella, and the Tertiary, 

 Q'lioyia and Mcsostoma. 

 Fig. m.-Aporrimu Parkm- The gcuus Ajwrrkciis, with various 

 (After J. related forms, constitutes a distinct 

 group, with strong alliances with the 

 StromUdce, and often raised to the rank of a distinct 

 family {Ajwrrhaidcv). The shell in Aporrhais (fig. 401) is 



soni. Cretaceous, 

 Starkie Gardner.) 



