NATURAL SCIENCES OF PHILADELPHIA. 185 
with one inner, long, bluntly bifid, stout, oblique cutting point, 
and two or more short outer cutting points. The same form of 
marginal is found in Pupa. 
The membrane is very peculiar in the lateral teeth, not only 
from their large size, but also from their symmetrical, tricuspid 
reflection, quite like the usual arrangement of central teeth in the 
Helicidex. 
Genus FERUSSACIA, Risso. 
The jaw (see pl. XVI., fig. 5 of that of the only species found in 
our limits, /. subcylindrica, Lin.) is low, slightly arcuate, wide, 
with but slightly attenuated, blunt ends; cutting edge with a 
slightly produced, wide, median projection ; anterior surface with- 
out ribs, but with fine vertical striz. There is a strong muscular 
attachment on its upper margin. 
Figure 28 gives the general arrangement of the teeth, the cha- 
F. subcylindrica. 
racters of the separate teeth being better shown on pl. XV., fig. 9. 
This figure, as well as that of the jaw, I drew from a Maine speci- 
men, furnished by Mr. Anson Allen. There were 24—1—24 teeth, 
with 8 perfect laterals. The central teeth are small and narrow 
in proportion to the laterals, with a long, narrow base of attach- 
ment, expanding at its lower angles. The reflected portion is 
very small, tricuspid; the central cusp stout, short; the side cusps 
small, blunt; all the cusps bear short cutting points. 
The lateral teeth are about as wide as high in their base of 
attachment, which is subrectangular. The whole upper edge is 
squarely reflected. The reflection is very short, and bears a stout, 
blunt, long, inner cusp, reaching almost to the lower edge of the 
base of attachment, and bearing along, blunt cutting point, which 
reaches beyond the lower edge. The outer side cusp of the reflec- 
tion is widely separated from the inner cusp, is very short, bluntly 
rounded, and bears a short, blunt cutting point. The first mar- 
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