CONCHOLOGIA! (CEST RICA: 61 
Shell very smali, cylindrical, tapering at both ends, 
white, shining; whorls 5-6, very oblique; 
C. exigquium, 
aperture oblique, oval, with a plait, on the Fig, 114, 
columella, and a slight one near to the open 
umbilicus ; lip thick, reflected, and flattened; 
lingual membrane with the rows of teeth 
slightly bent; buccal plate plain, slightly 
arched) TH. 6iZ,. W!, 37, mill. 

Lingual Dentition of C. exiguium, —| Morse. ] 
Fig, 115. 

Station, among chips, moss, etc., almost in the water. 
New Garden, Chester County; frequent. 
Family LIMNAEID&-. 
Shell variable, thin, horn color, usually with a slight 
fold on the columella; lip simple, acute. 
Animal, muzzle short, broad, dilated; tentacles con- 
tractile, flattened, subulate; eyes at their inner base; 
respiratory orifice on the right side. 
Station, fresh water; rising to the surface to breathe. 
Oss.— The Limnacide@ are generally sluggish animals; 
often preferring stagnant pools to clear running streams. 
They are herbivorous, feeding on the small confervoid 
plants which everywhere abound, in places which they 
inhabit. 
Their breeding season commences in the spring, and 
extends to midsummer. During this period, they are 
more readily found, and captured. In early autumn, 
they fill the pulmonary cavity with air, and soon disap- 
pear beneath the mud; still penetrating deeper, as the 
cold increases. 
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