HELICINA. 



Genus, the principal differences being in the general 

 form of the shells, in that of the apertures and in the 

 operculum. 



The Helicinae are generally nearly globular, some- 

 times, however, the spire is depressed and they have a 

 somewhat lenticular form, when very young they have an 

 umbilicus, of which, however, they do not retain the 

 slightest appearance when full grown ; their aperture is 

 rather triangular, the peritrcme being somewhat thick- 

 ened and reflected: the columella also is thickened, 

 nearly transverse, spread over that part which is usually 

 occupied by the umbilicus, its lower edge forming an 

 angle with the outer lip. Operculum generally testaceous, 

 rather triangular, not spiral, with a lateral nucleus. 



Only known in a recent state; the West India Islands 

 furnish by far the greater number of species hitherto 

 known; a few have been brought from the Islands in the 

 South Seas, and one is known as an inhabitant of North 

 America, namely the H. orbiculata.* One species which 

 has not yet been described, named by us carinata, appears 

 to abound in one of the Sandwich Islands, where the 

 natives formerly made various ornaments by stringing 

 them together. 



* Named by Say, Olygyra orbiculata. 



