130 



the body whorl with dull greenish and pale oehraceous ; and the 

 chesnut-brown color of the interior of the shell, combined with its 

 large dimensions, distinguish this species from all others yet die- 

 covered in this country. PI. 15, fig. 10.* 



Lymneus emarginatus, nob., from Lake Namakan, north of 

 Lake Superior ; collected by Dr. Bigsby. 



Lymneus elongatus, nob. Rainy Lake and Seine river, Dr. 

 Bigsby. 



Lymneus desidiosus, nob. Falls of Niagara. 



Physa heterostropha, nob. North-west Territory. 



Valvata sincera. — Shell subglobose-conic ; whorls nearly 

 four, accurately rounded, finely and regularly wrinkled across ; 

 aperture not interrupted by the penultimate whorl nor appressed 

 to it, but merely in contact with it, the labrum not diminished in 

 thickness at the point of contact ; umbilicus large, exhibiting the 

 volutions. 



Breadth less than one-fifth of an inch. Inhabits North-west 

 Territory. 



For this species I am indebted to Dr. Bigsby. It is very similar 

 to the tricarinata, nobis, but is destitute of carinated lines, and 

 the umbilicus is rather larger ; it differs from the ohtusa of 

 Europe, also, in the much greater magnitude of the umbilicus. 

 PL 15, fig. 11.* 



Paludina limosa, nob. North-west Territory. 



Ampularia depressa. — Shell ventricose, subglobular, obso- 

 letely banded with obscure green ; whorls four, slightly wrinkled ; 

 body whorl more prominent above, somewhat flattened towards the 

 suture, of a pale olivaceous color, which is almost concealed by 

 numerous, unequal, longitudinal and transverse greenish and brown- 

 ish lines ; spire very much depressed ; aperture suboval, within 

 somewhat glaucous, on the margin exhibiting the bands distinctly ; 

 labrum simple, as much rounded above as below ; umbilicus small, 

 nearly closed. 



Greatest width one inch and nine-twentieths. Total length one 

 inch and a half Length of the aperture one and one fifth of an 

 inch nearly. Inhabits East Florida. 



During an excursion to East Florida, in company with Messrs. 

 Maclure, Ord and T. Peale, I obtained a single dead and imperfect 



* [Plat« 74 of thiB reprint. — Ed.] 



