318 PLEUROTOM ARIID^. 



expanded, with depressed base ; aperture large, rounded, sub- 

 sin uated behind, pearly within ; columella re volute, acute ; lip 

 simple. 



Apparently not an operculated shell. The whole appearance, 

 especially the pearlj^ interior, reminds one of the Trochidse, and 

 Mr. Adams is evidently mistaken in referring it as he does to 

 the family Yalvatidse. 



Broderipia, Gray, 



Etym. — Named in honor of W. J. Broderip, Esq., the distin- 

 guished conchologist. 



Distr. — 3 species. Philippines, Grimwood's Island, South 

 Seas. — Cuming. B. iridescens, Brod. (Ixxxi, 19, 80). 



Shell minute, limpet-shaped, with a posterior submarginal, 

 non-spiral apex ; aperture oval, as large as the shell, brilliantly 

 nacreous. 



Velatnella, Vasseur. 



Etym. — Named after Charles Yelain, a French naturalist. 



Distr, — V. columnaris^ Vasseur (Ixxiii, 5). Eocene; Nantes, 

 France. 



Shell spiral, dextral, extremely elongated, thick and solid, 

 nacreous within ; aperture oval-oblique, peritreme continuous, 

 left margin with a slight columellar swelling. 



The nacreous interior brings this into the Trochidse, but it is 

 very distinct from any of the preceding forms. 



Family PLEUROTOMARIID^. 



Shell more or l^ss conically elevated, turreted or trochiform, 

 with a marginal slit in the upper part of the outer lip, or a row 

 of perforations in the upper part of the whorl ; aperture pearly 

 within. 



Pleurotomaria, Defrance. 



Etym. — Pleura, side, and tome, a notch. 



Distr. — 4 sp. West Indies, Moluccas, Japan, PI. Quoyana, 

 Fischer and Bernardi (Ixxxii, 84). Fossil, 400 sp. Cambrian to 

 Cretaceous; North America, Europe, Australia. 



Specimens from clay strata retain their nacreous inner layers; 

 those from the chalk and limestones have lost them, or t\xQj 

 are replaced by crystalline spar. Pleurotomarise with wavy 

 bands of color have been obtained in the carb. limestone of Lan- 

 cashire, In this extensive group there are some species which 

 rival the living turbines in magnitude and solidity, whilst others 

 are as frail as lanthina. 



Shell trochiform, solid, few-whorled, with the surface variously 

 ornamented ; aperture subquadrate, with a deep slit in its outer 



