CONCHOLOGIA CESTRICA. 53 
lip simple, with the margin thickened, and often rufous; 
lingual membrane, with 90 rows of 43 teeth, each; 
buccal plate slightly arcuate, with conspicuous longi- 
Lingual Dentition of Z. lubricoidea. — | Morse. 
Fig, 94. 

tudinal striae; cutting edge with an obtuse beak in the 
centres) El? 5) We 2, mall; 
Station, under the bark of decayed timber, and moist 
decayed leaves. Chester County; frequent. 
Oss. — This shell was, for a long time, supposed to 
be identical with the English species, Zwa lubrica, Miul- 
ler. To this opinion, the late Dr. Stimpson was the first 
to demur, on the score of its wide diffusion over this 
Continent; and a further examination, by Prof. E. S. 
Morse, tends to confirm the suggestion of Dr. Stimpson, 
as to its specific distinction. Fig. 95, @, represents an 
enlarged view of the central and lateral denticle of Zua 
lubricoidea, Stimp.; and Fig. 95, 4, the same denticles 
a, Dentition of Z.lubricoidea. b, Dentition of Z. lubrica,—| Morse. | 
Fig. 95. 
y\{-—_—1) 

68 
cf Zua lubrica, Mull. Our shell also differs in other 
respects from its foreign analogue. 
z % 
=) 
