786 PKOCEEDINGS OF THE NATIONAL MUSEUM. 



tQUADRULA BEADLEIANA Lea. 



* Unio beadleianus LEA, Pr. Ac. N. ci. Phila., V, 1861, p. 39; * Jl. Ac. N. Sci. 



Phila., V, 1862, p. 94, pi. xiv, fig. 242; *Obs., VIII, 1862, p. 98, pi. xiv, fig. 

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



* Margaron (Unio) beadleianus LEA, Syn., 1870, p. 5.~>. 



Mississippi to eastern Texas. 



tQUADRULA ASKEWI Marsh. 



* I'nio aslnri MARSH, Nautilus, X, 1896, p. 91; X, 1897, pi. i, figs. 3, 4. 

 Western Louisiana; eastern Texas. 



(Group of Quadrula trigona.) 



Shell triangular, generally inflated, with high, full beaks which are 

 incurved and turned forward over a well-developed lunule; anterior end 

 obliquely truncate above, often with a curved, shallow depression in 

 each valve running from the beaks to midway down the anterior end, 

 and forming a sort of secondary lunule ; posterior base usually incurved ; 

 the posterior ridge ending in a rather sharp point; beak sculpture, a 

 few coarse, concentric ridges turned upward behind and often swollen 

 on the posterior ridge, sometimes becoming finer and broken or irregu- 

 lar on th6 upper disk; hinge solid but not very wide; pseudocardiuals 

 triangular and radial, torn; there is a secondary lateral in the right 

 valve; cavity of the beaks generally deep and compressed; muscle 

 scars small, deep. 



Animal with the marsupium occupying the whole of all four bran- 

 chiae; inner gills generally free from the abdominal sac, much wider 

 than the outer in front; outer nearly or quite equaling them in width 

 behind ; anal opening distinctly crenulate or papillose. 



tQUADRULA RUBIGINOGA Lea. 



* Unio rubiginosus LEA, Tr. Am. Phil. Soc., Ill, 1829, p. 427, pi. vm, fig. 10; * Obs., 



I, 1834, p. 41, pi. vm, fig. 10.* DESHAYES, An. sans Vert., 2d ed., VI, 1835, 

 p. 548.* HANLEY, Test. Moll., 1842, p. 185; * Biv. Shells, 1843, p. 185, pi. xxi, 

 fig. 43. * CATLOW aud REEVE, Conch. Norn., 1845, p. 63.* H. and A. ADAMS, 

 Gen. Rec. Moll., II, 1857, p. 495.* CHENU, 111. Conch., 1858, pi. xnr, figs. 4, 4o, 

 46. * REEVE, Conch. Icon., XVI, 1865, pi. xxvn, fig. 136. * CALKINS, Pr. 

 Ottawa Acad. Sci., 1874, p. 44.* B. H. WRIGHT, Check List, 1888. *WAL- 

 TON, Moll. Monroe Co., 1892, p. 16, pi. vm, fig. 1. 

 "Margarita ( Unio) rubiginosus LEA, Syu., 1836, p. 20; 1838, p. 17. 



* Margaron ( Unio) nibiginosus LEA, Syu., 1852, p. 24; 1870, p. 37. 



* Unio rubiginosa DESHAYES, An. sans Vert., 3d ed., II, 1839, p. 672. 



* Quadrula rubiginosa BAKER, Moll. Chicago, Pt. 1, 1898, p. 77, pi. xix, fig. 2; 



xx, fig. 1. 



* Unio flatus CONRAD, New F. W. Shells, 1834, p. 69.* SAY. Am. Conch., VI, 



1834.* FERUSSAC, Guer. Mag., 1835, p. 27.* CONRAD, Monog., IX, 1837, p. 

 74, pi. XLI, fig. 2.* KUSTER, Conch. Cab., 1852, p. 61, pi. xiv, fig. 2 ; p. 265, pi. 

 LXXXIX, fig. 5.* CONRAD, Pr. Ac. N. Sci. Phila., VI, 1853, p. 249. 



* Unioflavus var. rubiginosus P.ETEL, Conch. Sam., Ill, 1890, p. 152. 



* Unio trigonus SOWERBY, Conch. Icon., XVI, 1868, pi. LXIV, p. 322. 



Entire Mississippi drainage; eastern Texas; St. Lawrence River 

 system; Nelson Kiver and its tributaries. 



