26 CONCHOLOGIA CESTRICA. 



Sub-genus MESODON, RAFINESQUE, 1831. 



Animal of Mesodon albolabris. [K. & B.] 

 Fig, 14, 



Shell sub- globose, or orbiculate-depressed ; umbilicus 

 open, or covered ; thin, finely striate, or decussate, 

 sculptured ; whorls 5 or 6, regular, aperture rounded, 

 or lunate, sometimes with a parietal tooth ; peristome 

 broadly reflected, white, margin rarely unidentate. 



M. albolabris, SAY. 



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



M. albolabris. [B. & B.] Jaw of M. albolabris. [Morse.] 



Fig, 15, Fig, 16, 



Shell large, convex, yellowish - brown, or russet ; 

 whorls 5 or 6, obliquely, fine-striate, with still finer 

 revolving striae, most distinct behind the reflected lip ; 

 lip broadly reflected, and flattened, closing the umbilicus 

 when mature; lingual membrane of 123 rows, of 44-1-44 

 teeth ; buccal plate heavy, arcuate, with ten large ribs, 

 crenulating the margins of the plate. H. 15, W. 25, mil- 

 limeters. Varies much in size. 



Station, rocky woodlands. Chester County, frequent. 



