794 



DIVISIONS OF THE GASTROPODA. 



comprised in it are Columbella (Tertiary and Recent), Cohimbellina 

 (Cretaceous), and Columbellaria (Jurassic and Cretaceous). 



Family 43. Purpurid^e. — In this family the shell is oval or fusi- 

 form, with a short spire. The columellar lip is expanded and more 



Fig. joz.—Ptirfiiira tetragona. Plio- 

 cene. (After Searles Wood.) 



Fig. 703. — Purpjiroidea nodulata. 

 Jurassic. (Copied from Zittel.) 



or less flattened, and there is a short anterior canal. The members 

 of this family are all marine, and the principal genera are Purpura, 

 Purpuroidea, and Rapana. 



In the genus Purpura (fig. 702) the shell has a short spire and 

 a large body-whorl ; the columellar lip is smooth and flattened ; 



Fig. 704.— Fusus Neocomiensis. 

 Lower Greensand. 



Fig. 705. — Fusus {Chiysodomus) con- 

 trarius. Pliocene (Red Crag). 



and there is a short oblique canal or notch in front. The genus is 

 exclusively Tertiary and Recent, and the fossil forms are few in 

 number. 



In the Jurassic and Cretaceous genus Pitrpuroidea (fig. 703) the 

 shell is oval and ventricose, with a short pointed spire and a large 



