CONCHOLOGIA CESTRICA. 



. Phil. Acad. [B/& B.J 

 Fig, 25. 



T. apprr.tsa. 



B. & B. 



T. appressa, SAY. 

 Helix appressa, Say, Jour 

 F. S., II., 1821. 



Shell much depressed, pale yellowish ; 

 whorls 5, often sub-angulated, with fine 

 transverse striae ; aperture contracted ; the 

 white, reflected, lip, close appressed at 

 base, and covering the umbilicus; the 

 inner margin of the lip, mostly with one or two teeth ; 

 an oblique, compressed, white, tooth on the 

 pillar lip ; lingual membrane with 105 rows, 

 of 40-1-40 teeth, each; buccal plate strongly 

 arcuate, the ribs, on the anterior surface, 

 denticulating both margins. H. 7, W. 17, 

 mill. 



Lingual Dentition of T. appressa. [B. & B.] 



Pig, 27, 



Jaw of T. 

 appressa. 



[B. & B.] 



Fig. 26, 



Station, under flat stones. On the Lehigh River, 

 Pennsylvania. 



T. tridentata, SAY. 



Helix tridentata, Say, Nich. Encyc., Amer. Ed., 1817. 



Shell very much depressed, light horn color, to 

 chestnut ; whorls 5 , obliquely acute-striate ; T . tride 

 aperture trilobate, contracted by a groove 

 behind the lip ; lip reflected, white, with 

 two acute, projecting, teeth, on its inner 

 edge; pillar lip with a strong, oblique, 

 tooth in the aperture ; striae converging 

 into the deep, open, umbilicus. H. 8, W. 

 15, mill.; very variable. 



Station, in fields bordering woods. Ches- 

 ter County. 



