of Rotella, (Pitonillus, Montf.,) as being inhabitants of 

 the ocean, with a much dilated basal callus. This union 

 led me to form my genus Oligyra for the reception of one 

 of the following species, well knowing it could not be 

 naturally congeneric with the Linnaean Trochus vesti- 

 arius, the type of that genus. 



In the Zoological Journal, for 1824, Gray has described 

 fifteen species, which he disposes in several minor groups ; 

 but Ferussac states, that he possesses from twelve to fif- 

 teen species which seem to be unknown to Gray, some of 

 which he could not refer to either of those groups. Not- 

 withstanding the variations and transitions of the species, 

 it may be found convenient and even natural to separate 

 generically, those in which the fissure is very obvious, in 

 the labrum, under the name of Helicina, from those of 

 which the labrum is simple or nearly so ; and to the latter 

 the name of Oligyra could be retained, under which 

 name I described the animal, 'till then entirely unknown. 



HELICINA ORBICULATA. 



SPECIFIC CHARACTEK. 



Shell pale greenish, or yellowish, with one or two bands. 



SYNONYM. 



Oligyra orbiculata. Nob. Nicholsons EnajcL 

 {Jimcr. 3(L Ed) 



