OBELISCUS. 241 



Distribution, tropical South America and the Greater An- 

 tilles. 



This extensive genus comprises all of the large American 

 Achatinidce except Neobeliscus calcareus, but also some species 

 no larger than Opeas or Subulina. It has not the free, over- 

 hanging columellar reflection of Opeas, nor the strongly trun- 

 cate columella of Subulina. A few of the smallest species 

 are clear corneous, but most of them are opaque and more 

 solid than Opeas. The reproduction is known to be vivip- 

 arous in some species of all the subgenera except Lyobasis, 

 in which nothing is known of the reproduction. Embryos 

 may often be shaken out of dry shells of the larger species 

 after soaking them to macerate the dry contents. 



Obeliscus was proposed for some nineteen species enumer- 

 ated above. Six of these, nos. 2, 6, 10, 13, 14, 19, are nude 

 names, introduced without description by Beck; no. 4 is type 

 of the prior genus Rumina; nos. 12, 15, 16, 18 have been re- 

 ferred to the later genus Opeas; and no. 3 belongs to the 

 genus Clavator. The remaining forms (0. calcareus, obelis- 

 cus, sylvaticus, subuliformis, septenarius, bacterionides) , are 

 referable to two genera, one containing the first species, 0. 

 calcareus, the other including the rest. Herrmannsen (Sept. 

 8, 1847) mentioned 0. calcareus as typical, and Gray (P. Z. 

 S., Nov., 1847) independently selected obtusatus; but the 

 principle that a tautonomic genus takes as type the species 

 upon which the generic name was based is one of such obvious 

 propriety, and has won such wide acceptance among natural- 

 ists in other departments of zoology, that I do not hesitate to 

 consider 0. obeliscus Spix as type of the genus Obeliscus. 



The name Obeliscus was used earlier by Humphrey for the 

 group of Trochus dolabratus Linne, but in an anonymous 

 catalogue, the Museum Calonnianum, not considered accept- 

 able as a source of nomenclature. 



The genus Stenogyra was proposed by Shuttleworth to in- 

 clude numerous turrited, unicolored, mostly pale or translu- 

 cent shelled forms, which had been placed in Bulimus and 

 Achatina by former authors. The group was so obviously 

 natural that it came at once into use, and it is only of late 



