MOLLUSCA. 



Pleurotoma demidiata, Broc. 



This genus, of which 500 species are now living, has a 

 fusiform shell with a long canal, and eyes at the base of 

 widely-separated tentacles. It is the type of the family 

 Pleurotomldse. Miocene, Soos, Austria. 



No. 267. Pleurotoma ttirricula, Broc. 

 Miocene Tertiary, Baden. 



No. 268. Conus striatulus, Broc. 



The large family Conidae are principally tropical. This genus dates from 

 the Cretaceous. Upper Pliocene, Colli, Artesi, Italy. 



No. 269. [608, Cast]. Rostellaria carinata, Mant. 



This genus belongs to the family Strombidse, and 

 was nearly twenty times more abundant in former 

 geological times than in our own; during the Creta- 

 ceous period it was represented by some very ex- 

 treme forms, of which the present specimen is one. 

 From the Gault, Folkestone, England. 



No. 270. Rostellaria fissurella, Lam. 

 Eocene, Grignon, France. 



No. 271. Aporrhais pes-pelicani. Lam. 



Only four species are living of this genus which has existed since the early 

 Jurassic. It belongs to the Strombidse. Quaternary, Palermo, Sicily. 



No. 272. Cassidaria echinophora. Lam. 



30 fossil forms of this genus of the Cassidse family are known from the 

 Cretaceous and later strata. Postpliocene, Ficarizzi, near Palermo, Sicily. 



No. 273. Pyrula bulbus, d'Orb. 



The genus is named from the thin, pear-shaped shell. Eight species are 

 still living. It is found in Cretaceous strata. Family Doliidis. Eocene, 

 Grignon, France. 



