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 

 Helicidae. 



Genus FERUSSACIA, Risso. 



The jaw (see pi. XVI., fig. 5 of that of the only species found in 

 our limits, F. 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 striae. There is a strong muscular 

 attachment on its upper margin. 



Figure 28 gives the general arrangement of the teeth, the cha- 



Fisr. 28. 



F. subcylindrica. 



racters of the separate teeth being better shown on pi. 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 Literals, 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 veiy 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- 

 13 



