190 TURBININ^. 



Ill the preparation of the following pages the characteristically 

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

 assistance to me. 



Key to genera and subgenera. 



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 . Mamwrostoma. 



b. operculum with spiral ribs outside 



shell imperforate, turbinate, elevated, solid . Callojjoma. 



shell imperforate, thin, depressed, granulose . Modelia. 



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



shell widely umbilicate, depressed . . . Ninella. 



V. operculum formed of club-shaped processes . Sarmatieus. 



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

 cleus. ......... Prisogasfer. 



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 cariuate 



operculum oblong, very convex . . . Paehypoma. 



operculum oval, 2-ribbed outside 



base flat or concave ..... Uvanilla. 



base somewhat convex, spire plicate . . Lithopoma. 



operculumjo-ribbed outside ..... Pomaulux. 



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



b. shell depressed, carinated, conic al)ove, convex below 

 polished, granulate, spines not projecting at sutures Chiildfordia. 

 not polished, spines projecting at sutures 



West Indian species Astralmm s. s. 



Oriental species Cyclocantha. 



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

 operculum with subcentral nucleus . . . . Bobna. 

 operculum with submarginal nucleus . . . Lithopoina. 



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

 with subcentral nucleus, concave in the centre outside. Leptothyra. 



