756 PROCEEDINGS OF THE NATIONAL MUSEUM. 



f PLEUROBEMA TROSCHELIANA Lea. 



* Unio troschelianua LKA, Tr. Am. Phil. >Soc., X, 1852, p. 280, pi. xxm, fig. 39; * Obs., 



V, 1852, p. 36, pi. xxin, fig. 39. * II. ami A. ADAMS, Gen. Rec. Moll., II, 

 1857, p. 496." B. II. WRIGHT, Check List, 1888.* P^ETEL, Conch. Sam., 

 Ill, 1890, p. 170. 

 *Margaron (Unio) troxthellanm LEA, Syn., 1852, p. 26; 1870, p. 40. 



Alabama River system. 



PLEUROBEMA IRRASA Lea. 



*Unio irrasus LEA, Pr. Ac. N. Sci. Phila,, V, 1861, p. 38; * Jl. Ac. N. Sci. Phila., 

 V, 1862, p. 91, pi. xm, fig. 239; *Obs., VIII, 1862, p. 95, pi. xin, fig. 239. 



* B. H. WRIGHT, Check List, 1888. 

 *Mar(iaron ( Unio) irrasus LEA, Syn., 1870, p. 38. 



Coosa Kiver system. 



| PLEUROBEMA ALTA Conrad. 



*Unio altus CONRAD, Jl. Ac. N. Sci. Phila., II, 1854, p. 298, pi. xxvn, fij,'. 5. 



* B. H. WRIGHT, Check List, 1888. t 



* Maryaron ( Unio) altus LKA, Syn., 1870, p. 42. 



t * Unio fibuloides LEA, Pr. Ac. N. Sci. Phila,, III, 1859, p. 154; Jl. Ac. N. Sci. 

 Phila., IV, 1859, p. 219, pi. xxvin, fig. 100; *Obs., VII, 1859, p. 37, pi. 

 xxvni, fig. 100. SOWERBY, Conch. Icon., XVI, 1866, pi. xu, fig. 223. 

 *B. H. WRIGHT, Check List, 1888. * P^TEL, Conch. Sam., Ill, 1890, p. 152. 



Margaron ( Unio) fibuloides LEA, Syn., 1870, p. 56. 



Connasauga River, Georgia. 



t PLEUROBEMA HARTMANIANA Lea. 



* Unio Jiartmanianus LEA, Pr. Ac. N. Sci. Phila., IV, 1860, p. 307; * Jl. Ac. N. Sci. 



Phila., V, 1862, p. 73, pi. vm, fig. 222; *0bs., VIII, 1862, p. 77, pi. vm, 

 fig. 222.* B. H. WRIGHT, Check List, 1888. 

 *Marqaron (Unio) liartmanianus LEA, Syn., 1870, p. 38. 



Coosa Kiver, Alabama. 



Dr. Lea lias shells in his collection from the Clinch River which he 

 places with this species, which I am certain belong to the Clava group. 



t PLEUROBEMA INSTRUCTA Lea. 



* Unio instructus LEA, Pr. Ac. N. Sci. Phila., V, 1861, p. 59 ; * Jl. Ac. N. Sci. Phila., 



V, 1862, p. 82, pi. x, fig. 230; *Obs., VIII, 1862, p. 86, pi. x, fig. 230. * B. H. 

 WRIGHT, Check List, 1888. 



* Margaron ( Unio) instructus LKA, Syn., 1870, p. 38. 



Cahawba River, Alabama. 



(Group of Pleurobema showaUerli.} 



Shell small, rounded triangular, inflated, slightly truncated ante- 

 riorly, posterior end arched and ending in a bluntly rounded point at 

 the po^t base, posterior ridge well defined; nmbonal region full; beaks 

 ratlin' prominent, the sculpture not observed; epidermis brown, not 

 rayed; hinge plate rather wide; pseudocardinals small, triangular, 



