69 



labrum also is a distinctive character; by comparison this part will 

 be perceived to be less arquatcd in its superior limb, than the cor- 

 responding part in dccisa. 



Paludina INTEGRA. — Shell olivaccous, pale, conic ; whirls six, 

 wrinkled across ; spire rather elongated, entire at the apex ; suture 

 profoundly indented; aperture subovate, less than half of the 

 length of the shell. 



Inhabits the waters of the Missouri. Length i inch. 



Very much resembles P. decisa, the spire, however, is more 

 elongated, and never truncated at the apex, but always acute. 



Paludina porata. — Shell obtusely-conic or subglobose ; volu- 

 tions four, convex, obsoletely wrinkled across ; spire obtuse ; labrum 

 and labium equally rounded, meeting above in a subacute angle ; 

 the upper edge of the latter appressed to the preceding whirl ; 

 umbilicus very distinct. 



Inhabits Cayuga Lake. Cabinet of the Academy. 



This species, which was found by Mr. Jessup, is rather larger 

 and more globose than P. limosa to which it is allied, and has a 

 more distinct umbilicus. It resembles P. decvpiens of Ferrussac, 

 but is much less acute, and rather smaller. 



Paludina lustrica. — Shell conic; whirls slightly wrinkled, 

 convex ; suture profoundly indented ; aperture oval, nearly orbi- 

 cular ; labrum with the superior edge not appressed to the pre- 

 ceding whirl, but simply touching it; umbilicus rather large, 

 rounded. 



Length, less than 1-10 of an inch. Cabinet of the Academy. 



The smallest species I have seen. The aperture somewhat re- 

 sembles that of a Valvata, to which genus it may probably be 

 referrible. Mr. Jessup obtained two specimens on the shore of 

 Cayuga Lake. 



Melania canaliculata. — Shell tapering, horn-color; volu- 

 tions about seven, slightly wrinkled ; spire towards the apex much 

 eroded, whitish ; body with a large obtuse groove, which is obso- 

 lete upon the whirls of the spire, in consequence of the revolution 

 of the suture on its inferior margin ; this arrangement permits the 

 superior margin of the groove, only, to be seen on the spire, in the 

 form of an obtuse carina on each of the volutions ; aperture bluish- 

 white within, with one or two obsolete revolving sanguineous lines ; 



