OF THE FAMILY OF NAIADES. 423 



tia, from which circumstance it is most probably in our cabi- 

 nets under another name. 



U. recta. This is the same with Barnes's pr3Elono;us. The 

 recta being described first should be retained. 



U. navijformis. This name cannot be retained, as Say had 

 previously described the shell under the name of cyVmdricus. 



U. glahrata. The habitat of this species is the Ohio river. 

 The description is too imperfect to identify it, and as the au- 

 thor acknowledges it has " nothing remarkable," we may fairly 

 conckide it to be a variety of some one of the numerous spe- 

 cies described, a cariosus most probably. 



U. nasuta. The author thinks this may be the nasufus of 

 Say, but the description answers much better to his own recta 

 or Barnes's gibbosus, and is no doubt one of those. I do not 

 believe the nasutus has ever been found in our western wa- 

 ters*. 



U. ovata is the ovatus of Say, and inhabits the western wa- 

 ters, not the Susquehanna and Mohawk, as mentioned by La- 

 marck. Maton and Rackett described a British shell under 

 this name, which I believe to be only a variety oS jncforum. 

 Those sent me from England by this name were certainly 

 mere varieties of the pictorum. 



U. rotundata. In most of our cabinets may be found a 

 beautiful shell, which we have thought to be of this species, 

 and have adopted the name. It does not, however, answer 

 to the description in some essential characters, and I have 

 therefore thought proper to describe the American shell, and 

 give it a new name. (See description of cir cuius.) Lamarck 

 gives no habitat. Ours is from the Ohio, 



U. littoralis is from the Seine, and is described by Drapar- 

 naud, who says it resembles the "fZ margaritifera,'\ but is 

 much smaller. 



U. semirugata. Description too short to identify it. Has 

 no habitat. 



* Swainson says, " The Unio nasuta, however, of Lamarck, I apprehend, will 

 be found different" from Unio nasutus of Say. — Zool. Fllus. Vol. I. pi. 57. 

 VOL. III. 5 F 



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