296 CONRAD'S NEW SPECIES OF tJNIO. 



U. NapeaKensis. Pi. 26, fig. 4.-^Oblong-suboval ; anterior margin regularly rounded ; posterior margin 

 obtusely rounded and nearly direct, extremity acutely rounded and situated but little above the basal 

 line; ligament and basal margins parallel; basal margin slightly contracted; disk contracted obliquely 

 from beak to base; umbo with irregular angulated -wrinkled plicJE concentrically arranged ; epidermis 

 blackish-brown, obscurely rayed towards the base; within bluish white, with wax-colored stains; 

 cardinal teeth compressed, inclining to be double iii each valve. 



This species was described and figured by Lesson, with some doubt, as the depressa 

 of Lam., but the original of that species, figured byDelessert and Chenu, is a very 

 different shell, and has a singular resemblance externally to U. sukidens, a variety of 

 complanatus, as figured by Chenu on the same plate with depressa. 



D'Orbigny's depressa, a South American shell, must be a very different species 

 from Lamarck's. 



U. HEBETATUS. PI. 26, fig. 5. — -guboval, slightly ventricose; disks slightly but widely contracted; umbonal 

 slope obtusely angulated ; anterior margin obliquely truncated above the extremity ; umbo wide, obtuse; 

 posterior margin obtusely rounded, direct; extremity obtusely rounded; epidermis dark yellowish 

 brown, glossy, rough and wrinkled posteriorly; within white; cardinal teeth sulcated; one thick tooth 

 in the right valve, and two diverging teeth in the other, the anterior one sharp, the posterior one thick 

 and directed towards the posterior extremity ; lateral teeth straight, elevated, and finely striated 

 obliquely. 



Locality. From Missouri. 



Two specimens of this very distinct species are in the collection of the Academy. 

 It bears a distant resemblance to U.Jlavus, Raf., but is much more obtuse posteriorly, 

 with a darker and more wrinkled epidermis, &c. 



U, RIVULARIS. 



U. declivis, Con. (not Say.') Alonography of Unionidae, p, 45. PI. 23, fig. 1. 



This species differs from declivis, in being more convex, in having more prominent 

 beaks, in wanting the subrostrated posterior end, and especially in having much 

 thicker and more elongated cardinal teeth. It is also a larger species. It belongs 

 to a group which I have named Uniomerus- 



U. . PI. 26, fig. 6. 



This figure represents a shell sent from Australia in company with U. Napeanensis, 

 Balo?inensis, &c., labelled Bogan river. It cannot be distinguished from a common 

 variety of U. complanatus, yet if it inhabits an Australian river it must be a different 

 species. 



U. PORRECTUS. PI. 26, fig. 7. — oblong or subfliomboidal, convex, slightly contracted from beak to base; 

 hinge and basal margins parallel, nearly rectilinear ; posterior margin oblique, extremity obtusely 

 rounded ; epidermis dark olive brown ; within white ; cardinal teeth oblique> double in each valve ; 

 cardinal area under the beaks almost obliterated. 

 U. paraUelus, Con. Proceed. Acad. Nat. Sci. i. p^. 20. 



Locality Jackson, Miss^ 



