THE EOCENE PERIOD. 



303 



of them belong to that great section of the Gasteropods in 

 which the mouth of the shell is notched or produced into 

 a canal (when the shell is said to be " siphonostomatous ") 

 this section including the carnivorous and most highly-or- 

 ganized groups of the class. Not only is this the case, but 

 a large number of the Eocene Univalves belong to types 

 which now attain their maximum of development in the 

 warmer regions of the globe. Thus we find numerous species 



Fig. 216. Cardita planicoata. Middle Eocene. 



of Cones (Conus), Volutes (Valuta}, Cowries (Cypraa, fig. 218), 

 Olives and Rice-shells (Oliva), Mitre-shells (Mitra), Trumpet- 

 shells (Triton}, Auger-shells (Terebra), and Fig-shells (Pyrula}. 

 Along with these are many forms of Pleurotoma, Rostellaria, 

 Spindle-shells (Fusus}, Dog- whelks (Nassa}, Murices, and many 

 round-mouthed ("holostomatous ") species, belonging to such 



Flfir; m.Typhis tubifer, a " slphonosto- 

 matous " Univalve. Eocene. 



Fig. 218. Cyprcta 

 elegant. Eocene. 



genera as Turritella, Nerita, Natica, Scalaria, &c. The genus 

 Cerit hium (fig. 219), most of the living forms of which are 



