232 
subangular, generally distinct, and sometimes separate from tlie 
body whorl, and usually furnished with teeth. 
Ohs. The shells belonging to this genus have been divided, with 
much propriety, from the Linnaean genus Turbo ; they inhabit 
moist places, under the bark of trees, under stones, moss, &c. ; many 
of them are sinistraL 
Helicina.* — -Shell subglobular ; spire depressed, or but little 
elevated ; aperture semiorbicular, modified by the preceding volu- 
tion ; base with a more or less obvious callosity covering the um- 
bilicus 3 labrum acute or a little reflected; columella at base a little 
prominent, and joined to the labrum at an angle ; operculum horny, 
and with concentric elements. 
Animal terrestrial, globular, subspiral ; head rostrated ; rostrum 
bilabiated, at the tip end shorter than the tentacula, which are two 
in number, filiform, and have the prominent eyes at the exterior 
part of their base, upon a tubercle ; the organs of respiration as in 
Gydostoma'j the branchial cavity communicates with the atmos- 
phere by a large slit ; foot simple, with an anterior marginal groove. 
Ohs. The general appearance of the shell resembles much that 
of a Helixy but the base of the columella is a little prominent, and 
the locality of the umbilicus is more obviously covered with a cal- 
lus. But the most striking difference is in the animal, which in 
Helix has the eyes at the tip, of the superior pair of tentacula, 
whereas in Helicina they are at the exterior base of the only pair ; 
the operculum of the latter is also a sufl[icient distinction. 
Lamarck formerly united several species under this genus that 
he has since very properly separated under the name 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 Linnman 
Troclms vestiarius, the type of that genus. 
In the Zoological Journal, for 1824, Gray has described fifteen 
species, which he disposes in several minor groups ; but Ferrussac 
states, that he possesses from twelve to fifteen species which seem 
to be unknown to Gray, some of which he could not refer to either 
of those groups. Notwithstanding the variations and transitions of 
the species, it may be found convenient and even natural to sepa- 
[* Am. Con. v,— E d,] 
