NO. 1205. SYNOPSIS OF THE NAIADES— SIMPSON. 773 



Section QTTADRTJLA (Rafinesque, 1820) Agassiz. 



(Type, Unio cylindricus Say.) 



Shell rhomboid; surface pustulous, with a high, rounded, or sharp 

 posterior ridge; epidermis generally smooth and bright. 



(Group of Quadrula metanevra.) 



Shell quadrate or rhomboid, with a wide, rounded posterior ridge, 

 above which, on the posterior slope is a decided radial furrow; whole 

 surface except the anterior end generally pustulous, the sculpture of 

 the posterior slope being often wrinkled; umbonal region high; epi- 

 dermis shining, usually painted with a beautiful pattern of triangular 

 spots, and sometimes chevron -shaped lines ; hinge strong, the secondary 

 lateral in right valve rather feeble, but there is often a faint third lat- 

 eral above; cavity of the beaks deej) and compressed. 



Animal with the marsupium filling all four leaves of the branchiae, the 

 ova giving it a jjurplish tint; inner gills free from the abdominal sac for 

 the greater part of their length ; mantle bordered with black ; branchial 

 opening opposite the lobe of the shell, extending well on to its base; anal 

 opening without papillae. 



tQUADRULA CYLINDRICA Say. 



*Unio cylindricus Say, Nicli. Encyc, II, 1816, pi. iv, fig. 3. — "■ Hildreth, Am. Jl. 

 Sci., XIV, 1828, p. 283, figs. 13, 136.—* Short and Eaton, Transylvania Jl., 

 1831, p. 76.—* Say, Am. Conch., VI, 1834.—* Conrad, New F. W. Shells, 1834, 

 p. 68.— *Feeussac, Guer. Mag., 1835, p. 27.— *Hanley, Test. Moll., 1842, 

 p. 182; *Biv. Shells, 1843, p. 182, pi. xx, fig. 31.— *Catlow and Eeeve, 

 Conch. Nom., 1845, p. 58.—* Conrad, Pr. Ac. N. Scl. Phila., VI, 1853, p. 248.— 

 *H. and A. Adams, Gen. Rec. Moll., II, 1857, p. 496. — *Kuster, Conch. Cab. 

 Unio, 1861, p. 194, pi. lxii, figs. 1, 2.— *Sowerby, Conch. Icon., XVI, 1867, 

 pi. LX, fig. 300.— *B. H. Wright, Check List, 1888.— *P.etel, Conch. Sam., 

 Ill, 1890, p. 150.— * Call. Tr. Acad. Sci. St. Louis, VII, 1895, p. 15, pi. xii. 



* Margarita (Unio) cylindricus Lea, Syn., 1836, p. 17; 1838, p. 16. 

 * Margaron {Unio) cylindricus Lea, Syn., 18.52, p. 23; 1870, p. 35. 



* OrUionymuH cylindr'icus Agassiz, Arch. fiir. Naturg., I, 1852, p. 48. 

 ^ Mya cylindrica Eaton, Zool. Text-Book, 1826, p. 219. 



* Unio {Theliderma) cylindrica Swainson, Treat, on Mai., 1840, p. 271, fig. 54c. 



* Unio (Eurynia) solenoides var. cylindrica JiAFiNESQVK, Ann. Gen. Sci. Phys. Brux., 



V, 1820, p. 298. 



* Unio naviformis Lamarck, An. sans Vert., VI, 1819, j). 75. — *Deshayes, Encyc. 



Mi^th., II, 1830, p. 580.—" Valenciennes, Rec. Obs. Zool., II, 1833, p. 233, pL 

 Liii, fig.4.— *Deshayes, An. sans Vert., 2d ed., VI, 1835, p. 537; 3d ed., II, 

 1839, p. 669.— *Anton, Verz. der. Conch., 1839, p. 14.— * Reeve, Conch. Syst., 

 1841, p. 118, pi. Lxxxix, fig. 7.' 



* Unio rugosus Chenu, Man., 1859, II, p. 138, fig. 668. 



Entire Ohio, Cumberland, and Tennessee river systems; west to 

 Nebraska (Aughey, doubtful) ; south to Arkansas and Indian Territory. 



'Mr. B. H. Wright, Nautilus, XII, 1898, p. 6, has made a var. strigillatus of a com- 

 pressed, very rough form of cylindrica. There seems to me to be an absolute grada- 

 tion from cylindrical, nearly smooth specimens to this form. 



