28 CONCHOLOGIA CESTRICA. 
angular; lip narrowly reflected, white, slightly thick- 
ened, internally, at base ; umbilicus closed, but indented. 
Yellow horn color. H. 10, W. 18, mill. 
Station, under logs, in woods. Western Pennsylvania. 
M. clausa, Say. 
Helix clausa, Say, Jour. Acad. Nat. Sci. F. S., 1821. 
M. clausa, Shell sub-globose, light yellowish-brown ; 
"Pip. 20, whorls 5, finely striate; aperture rounded, 
e contracted; lip reflected, flat; umbilicus 
narrow, and partly covered by the reflection 
of the lip. H.9, W. 16, mill. 
Station, under logs, etc. New Garden, 
Chester County ; rare. 
Oss. — This so nearly resembles some edentate forms 
of the next species, as to occasion difficulty. 

M. thyroides, Say. 
Helix thyroides, Say, Nich. Encyce., Amer. Ed., 1817. 
IM, thyroides, —|{B. & B.] 

Shell depressed- globular, pale yellowish - brown; 
whorls 5, with fine transverse striz; aperture rounded ; 
pillar lip with a prominent, oblique, white tooth; lip 
widely reflected, sometimes with its face grooved; yel- 
lowish exterior; umbilicus small, partly covered. H. 
12-14, W. 20-25, mill. 
Station, in woods, gardens, and among decayed wood. 
Chester County. Often confounded with the next. 
