MANUAL OF THE MOLLUSCA. 



8 hell like Ccecum, smooth. ; aperture simple, acute ; apex closod 

 by a mamillated plug ; operculum, convex. 



Distribution, 2 species. Europe, West Indies, Mazatlan. 



Meioceras, Carpenter. 



Etymology, meion, rather small ; ceras, horn. 

 Young shell spiral or flat ; adult somewhat inflated ; aperture 

 oblique ; operculum spiral, scarcely concave. 

 Distribution, 3 species. "West Indies. 



Strebloceras, Carpenter, 1858. 



Etymology, streblos, twisted; ceras, horn. 



Shell with the spire not decollated, no plug formed ; nuclear 

 whorls orbicular, perpendicular to the plane of the adult ; the 

 plane of growth is flat, as in Ccecum, but some examples have a 

 slight twist, forming an approach to Meioceras. 



Fossil, 4 species. Eocene. Hampshire, Paris. 



Family Y. — Turritellid^* 

 Includes Turritella, Proto, Mesalia, and 



Cassiope, Coquand, 1865. 



Synonym, Omphalia, Zekeli, 1852 (non Omphalius, Philippi, 

 1847). 



Example, Turritella Eenauxiana, D'Orbigny. 



Shell thicker, and with more rapidly increasing whorls than 

 in Turritella, often pupiform ; aperture rounded, continuous ; 

 outer lip notched or sinuated by an impressed furrow, which 

 winds round the last whorl ; columella usually distinctly um- 

 bilicated. 



Distribution, 32 species. Cretaceous. Europe, India, and 

 America. 



[Family ScALARiADiEf ] 



Includes Scalaria and the sub-genera Eglisia, Pyrgiscus, and 

 Cirostrema, Morch. 

 Shell solid, varices irregular, whorls generally cancellated. 



Cochlearia, Braun. 

 Synonym, Chilocyclus, Bronn. 



* See p. 248. t See p. 250. 



