OBELISCUS. 243 



<l<a may be the result of a later radiation than that which 

 separated Obeliscus and Protobeliscus. 



Key to Subgenera of Obelise as. 



NOTE. Keys to the species may be found under the sub- 

 generic heads. 



I. Embryonic shell with a convexly-conic spire and sub- 

 acute apex, the columella .straight, not truncate. Adult 

 shell thin, smoothish, sinistral, very long, composed of 12 

 to 15 whorls. Antilles. 



Subgenus PSEUDOBALEA, species 29, 30. 



II. Embryonic shell with globose or hemispherical spire, flat- 

 tened at the summit; shell dextral. 



a. Columella of the embryonic shell entire, not trun- 

 cate or excised below (pi. 37, f. 100) ; adult shell 

 dextral, smootliish or finely striate, usually large. 

 South America, 



Subgeiius OBELISCUS s. str., species 1 to 8. 

 aa. Columella of the embryonic shell more or less trun- 

 cate or excised at base (pi. 37, figs. 102, 103) ; adult 

 shell smoothish, not rib-striate. 



b. Columella of the adult with reflexed edge, not 

 calloused. Andean. 



Subgenus PROTOBELISCUS, species 9 to 17. 

 bb. Columella of the adult calloused below. An- 

 tilles. Subgenus STENOGYRA, species 18 to 28. 

 aaa. Columella of the embryonic shell unknown; adult 

 shell small, ribbed or rib-striate, two embryonic 

 whorls of the globose summit smooth. Western 

 Cuba. Subgenus LYOBASIS, species 31 to 36. 



The limits of the groups Obeliscus s. sir., Stenogyra and 

 Protobeliscus have not been marked out in detail, because the 

 essential differences of the first two are in the embryonic 

 shells, which are known in but few species. In general, Obe- 

 liscus is Brazilian, Protobeliscus Andean, and Stenogyra is 

 Antillean. 



Numerous species which have been described or mentioned 



