QUADRULA 889 
Ohio, Cumberland, and Tennessee River systems ; southwest 
to Arkansas; west to Nebraska’; north in the Mississippi to 
Prairie du Chien, Wisconsin. 
Type locality, Ohio. 
Unio pyramidatus Lea, Tr. Am. Phil. Soc., [V, 1834, p. 109, 
pl. xvi, fig. 39; Obs., I, 1834, p. 119, pl. xvi, fig. 39.—Han- 
LEY, Biv. Shells, 1843, p. 186, pl. xx, fig. 45—DESHAYES, 
Traite Elem..de Conch., II, 1850?, p. 216, pl. xxxz1, figs. 1, 2. 
—CHENJ, III. Conch.» 1858, pl. xvi, figs. 5, 5a, 5 —SowEr- 
By, Conch. Icon., XVI, 1868, pl. Lxrv, fig. 323. 
Margarita (Unio) pyramidatus Lea, Syn., 1836, p. 21 ; 1838, p. 
17. 
Margaron (Unio) pyramidatus Lea, Syn., 1852, p. 25; 1870, p. 
39. 
Quadrula pyramidata SIMPSON, Syn., 1900, p. 790. 
Pleurobema pyranidatum OrtMANN, Ann. Car. Mus., VIII, 
1912, p. 264. 
Umio mytiloides Desuayes, Enc. Meth., II, 1830, p. 586, pl. 
CCXLIX, fig. 4—ConraAp, Monog., IV, 1836, p. 41, pl. xx.— 
Swainson, Treatise on Mal., 1840, p. 267, figs. 52-53.— 
Muster= Conch. Cab 1852, p> 50; pl. xu, ‘fig. 3; 1861, p: 
265, pl. LXXXIXx, fig. 4. 
Margarita (Unio) mytiloides Lea, Syn., 1836, p. 21; 1838, p. 
17. 
Margaron (Unio) mytiloides Lea, Syn., 1852,, p. 25; 1870, p. 
39. ‘ 
Unio mytiloides Rafinesque var. pyramidatus Pavre., Conch. 
Sam., IIT, 1890, p. 160. 
Unio cardiacea GUERIN, Icon. Regne Animal, 1828?, IT, pl. 
SRV, ees 7. 
Unio ruber Conran, Pr. Ac. N. Sci. Phila., VI, 1853, p. 257. 
Unio obliqua Woon, Ind. Test. Rev., 1856, p. 200, pl. 1, fig. 8. 
Differs from allied forms in its great obliquity and in usually 
having rose-colored nacre. The young shells are not nearly 
so oblique. 
Ortmann, (1. c.), states that only the outer gills are mar- 
supial and savs that “this is only an extreme form of P. 
obliquum.”? 
