inhabiting the United States. 355 
identical; but on the lower surface the resemblance 
no longer holds, for, though the aperture is nearly the 
same, the umbilicus of that species is never closed, 
and it never attains the size of the present spe- 
cies. Varieties of the type are caused by the ab- 
sence of the upper or lower lip-tooth, or of both, the 
want of the raised projections of the epidermis, and 
of the transverse striæ, and by the great depression 
of the spire in some individuals, which produces 
a distinct angle or carina on the outer whorl. This 
last. variation, which brings it within the genus 
CanocóLLA of Lamarck; is found in other species, 
especially in their immature state, and shows that 
the distinctive characters of that genusa ve not to 
be depended on. 
A carinated variety, which was aaa br Mr. Say 
as “ a variety with a very “prominent acute carina, 
destitute of minute protuberances,” has been de- 
scribed by Mr. Lea as CanocoLLA Aelicóides. The 
same was figured by Férussae, Pl. 50, A. fig. 7. A 
strongly carinated variety, with a single tooth on the 
outer lip, and smooth epidermis, was described by 
Mr. Say as H, obstricta. Another variety, having 
the oblique striæ widely separated and very distinct, 
and being at the same time carinated, has been de- 
scribed by Mr. Lea as H. Carolinénsis. An exami- 
nation of the specimens from which these descriptions 
were made, has convinced me that they are only 
varieties. 
Mr. Say’s description was published in January, 
1821, and the shell has been known in the United 
States by the name of H. palliàta, since that time. 
