GASTEROPODA. 



13 



from which nearly three hundred species are known. The 

 maximum, however, is attained in existing seas, in which 



Fig. 392. — A, Oliva Branderi— 'Eocene ; b, Anmllaria glandina— 'Eocene ; c, Conus deperdiUis 

 — Eocene ; d, Pleurotoiwa rostrata — Eocene. 



there are very numerous species. Borsonia, dating from the 

 Eocene, is near the preceding, but has an obliquely-folded 

 columella. 



Fam. 5. VoLUTiD^. — Shell turreted or convolute, the 

 aperture notched in front ; the columella obliquely plaited. 

 No operculum. Foot very large ; mantle often reflected 

 over the shell. The living members of the Volutidce are 

 chiefly inhabitants of warm seas, and are often remarkable 

 for their brilliant colours. The family does not appear to 

 have existed till towards the later portion of the Cretaceous 

 period ; but it is abundantly represented in the Tertiaries, 

 and attains its maximum in existing seas. The most im- 

 portant genera are Voluta and Mitra. 



The true Volutes form the genus Vohda (fig. 393), charac- 

 terised by the short spire, large, deeply-notched aperture, and 

 columella with several plaits. Species of Vohda occur in 

 the Cretaceous period, but the genus is mainly Tertiary and 



