' LIMN^A. 65 



The perforation, too, is smaller, and the columella more curved. The two 

 specimens before me have the superior whirls black from the deposit of 

 the oxide of iron. The aperture is about half the length of the shell. 

 (Lea.) 



I.imnna plica. Lea. — Shell turreted, rather thin, yellow, striate, imper- 

 forate ; spire rather elevated ; sutures impressed ; whirls five, 

 convex ; aperture small elliptical. Fig. 103. 



Hah. Tennessee: Dr. Troost. My cabinet, and cabinet of Dr. 

 Troost. Diam. .18, length .38 of an inch. 



A small species with a large incurved fold. It resembles L. 

 exigua, herein described, in size, but in the form of the colu- Limnaa 

 mella it is entirely different. The aperture is about half the pUca. 

 length of the shell. 



Limnsea planulata, Lea. — Shell ovately conical, thin, smooth, subdi- 

 aphanous, brown, perforate ; spire rather short ; sutures im- 

 pressed ; whirls five, convex ; aperture small, ovate. Fig. 104. 



Hub. White Sulphur Springs, Virginia : P. H. Nicklin. My 

 cabinet, and cabinet of P. H. Nicklin. Diam. .15, length .35 

 of an inch. 



Several specimens of this small species are before me, one 

 of them considerably larger than the others and possessing one 

 more whirl. The whirls are inflated, but flattened in the middle. 

 This gives a roundness to their superior part. The perforation 

 is small and the fold scarcely observable. The aperture is less than half 

 the length of the shell, and contracted. (Zea.) 



Limnsea exigua, Lea. — Shell subfusiform, thin, striated, diaphanous, pale 

 yellow, perforate ; spire rather short ; sutures impressed ; whirls 

 five, rather convex ; aperture elliptical. 'Em. 105 



Hub. Tennessee : Dr. Troost. My cabinet, and cabinet of 

 Dr. Troost. Diam. .15, length .35 of an inch. 



This is a small species about the size of L. plica, herein de- 

 scribed, and in outline resembling it. It difi'ers, however, 

 altogether, in the columella, which is nearly, and the fold 

 scarcely observable. The aperture is about one-half the length 

 of the shell, and contracted at the lower part. {Lea.) 



Limnma 

 exigiui. 



Limnxa rustica', Lea.' — Shell subfusiform, thin, imperforate ; Fig. 106. 

 sjjire rather elevated; sutures impressed; whirls five, rather 

 convex ; aperture narrow elliptical. 



Hab, Poland, Ohio : Dr. Kirtland. My cabinet, and cabinet 

 of Dr. Kirtland. Diam. .15, length .35 of an inch. Limnaa 



A single specimen only of this was received with some other rustica. 



' H. & A. Adams (II, 253) catalogue a Ltmnxn rustica, Andrz, but 

 whether it has priority of publication or not, I do not know. 



