786 PBOCEEDINGS OF THE NATIONAL MUSEUM. 



tQUADRULA BEADLEIANA Lea. 



* Unio leadleianus Lea, Pr. Ac. N. Soi. PMla., V, 1861, p. 39; * Jl. Ac. N. Sci. 



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

 242.—* B. H. Wright, Check List, 1888. , 

 " Margaron (Unio) headlelanus Lea, Syn., 1870, p. 55. 



Mississippi to eastern Texas. 



tQUADRULA ASKEWI Marsh. 



* Unio askeivi 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 uj)ward behind and often swollen 

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

 lar on the upper disk; hinge solid but not very wide; pseudocardinals 

 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 RUBIGINOSA Lea. 



* Unio rubiginosus Lea, Tr. Am. Phil. Soc, III, 1829, p. 427, pi. viii, fig. 10; * Obs., 



I, 1834, p. 41, pi. VIII, 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 and Eeeve, Conch. Nom., 1845, p. 63.—* H. and A. Adams, 

 Gen. Eec. Moll., II, 1857, p. 495.—* Chenu, 111. Conch., 1858, pi. xiii, figs. 4, 4a, 

 4&.—* Reeve, Conch. Icon., XVI, 1865, pi. xxvii, 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. viii, fig. 1. 



*Margarita ( Unio) ruhigitiosus Lea, Syn., 1836, p. 20; 1838, p. 17. 



*Margaron ( Unio) ruUginosiis Lea, Syn., 1852, p. 24; 1870, p. 37. 



*Unio ruhiginosa Deshayes, An. sans Vert., 3d ed., II, 1839, p. 672. 



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



XX, fig. 1. 

 *Unio flavus 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. 

 ""Unio flavus var. riibiginosus P^-etel, Couch. Sam., Ill, 1890, j). 152. 



* Unio trigonus Sowerby, Conch. Icon., XVI, 1868, pi. LXiv, p. 322. 



Entire Mississippi drainage; eastern Texas; St. Lawrence River 

 system ; Nelson Eiver and its tributaries. 



