190 TURBISINjE. 



In the preparation of the following pages the characteristically 

 careful and reliable work of Dr. Paul Fischer has been of constant 

 assistance to me. 



Key to genera and sub genera. 



I. Shell turbinate or depressed, convex below, young not spinose ; 

 operculum convex outside, usually smooth or granulose, sometimes 

 with concentric ribs, nucleus near the centre. 



a. operculum simply convex, smooth or granulose 



shell turbinate, spire exserted .... Turbo, s. s. 

 shell depressed above, produced at base . Marmorostoma. 



b. operculum with spiral ribs outside 



shell imperforate, turbinate, elevated, solid . Callopoma. 



shell imperforate, thin, depressed, granulose . Modelia. 



shell imperforate, thin, depressed, smooth . . . Ocana. 



shell widely umbilicate, depressed . . . Ninella. 



c. operculum formed of club-shaped processes . Sarmaticw. 



II. Shell turbinate, oval, solid ; operculum with submarginal nu- 

 cleus. ......... Prisogaster. 



III. Shell trochiform, flattened above or below, young carinated 

 and spinose ; operculum with submarginal or terminal nucleus, 

 generally with ribs outside. 



a. shell conic, flat or concave below 



imperforate, periphery rounded, base concave . . Cookia. 

 imperforate, periphery carinate 



operculum oblong, very convex . . . Pachypoma. 

 operculum oval, 2-ribbed outside 



base flat or concave Unntllfa. 



base somewhat convex, spire plicate . . Lithopoma. 



operculum 3-ribbed outside ..... Pomaulax. 



umbilicate, base concave . . . . . . Imperator. 



b. shell depressed, carinated, conic above, convex below 

 polished, granulate, spines not projecting at sutures Guildfordni. 

 not polished, spines projecting at sutures 



West Indian species Astralium s. s. 



Oriental species Cycloccuitha. 



c. shell turbinate, not flat below, periphery not carinate 

 operculum with subcentral nucleus .... JSolma. 

 operculum with submarginal nucleus . . . Lithopoma. 



IV. Shell turbinate or globose, small, solid ; operculum multispiral, 

 with subcentral nucleus, concave in the centre outside. Leptothi/m. 



