999, - PROCEEDINGS OF THE ACADEMY OF 
of attachment and bearing one inner, long, oblique, acutely bifid 
cutting point, and one shorter, outer, sometimes bifid, side cutting 
point. 5 
The only other Pomatia whose dentition has been figured is 
H. pomatia, which shows the same type of teeth (Goldfuss, 1. ¢. 
pl. IV., fig. 6). The jaw of numerous European species is known, 
and of the same type as in aspersa. 
(3) Jaw with delicate, distant ribs to its anterior surface, usually running 
obliquely to the median line. 
Genus CYLINDRELLA, Pfr. 
ie aw as in Macroceramus, described below. 
Lingual membrane of our two species C. jejuna and C. Poeyana 
not examined byme. The dentition of the genus is very peculiar. 
The membrane is exceedingly long and narrow. The base of 
attachment of the centrals is small, long, narrow, with the upper 
margin broadly reflected into a blunt, rounded and expanded 
gouge-shaped cutting point; the laterals have a long, subquad- 
rangular base of attachment, bearing below, a large, bluntly 
rounded, greatly expanded, palmate cusp, representing the inner 
and central cusps of the laterals; and, above, a long, slender, graceful 
extension, representing the external cusp of the other Helicide. 
This last is bluntly truncated, or bears a recurved cusp smaller 
but of same shape as that below; or it has a laterally extended, small 
blunt point. In some species the laterals 
extend to the margin of the lingual mem- 
brane ;' in others there are distinct marginal 
e teeth, long, narrow, laminar, with bluntly 
recurved apices. A full description and 
a a figures of these various forms of teeth will 
he be found in Journal de Conchyliologie, 
January, 1870. 
I here give a figure of the dentition of one 
only of these types represented by the 
membrane of C. sceva. 
ne ee 
Lingual dentition of 
Cylindrella sceva. [Bland.] 
1 Probably this is the case in our species, asit is so in the allied C. elegans. 
See pl. XX., fig. 6 
Since the above was written, I find my anticipations realized in the case 
of 0. Poeyana. Specimens from Key West collected by Mr. W. W. Cal- 
kins, have 14—1—14 teeth of same type as in elegans. There are over 40 
ribs on the jaw. 
