HO. 1205. SYNOPSIS OF THE NAIADES SIMPSON. 573 



II, 1857, p. 492. *SOWERBY, Conch. Icon., XVI, 1868, pi. LXVI, tig. 336. 



* B. H. WRICIIT, Check List, 1888. -" P.KTKL, Conch. Sam., Ill, 1890, p. 149. 



* FISCHER and CROSSE, Miss. Sci., Pt. 7, II, 1894, p. 615. 

 "Margarita ( Unio) cnprinus LEA, Syn., 1836, p. 39; 1838, p. 25. 

 *Mar{iaron (Unio) cuprinus LEA, Syn., 1852, p. 38; 1870, p. 61. 



* Unio acretis REEVE, Conch. Icon., XVI, 1856, pi. xxx, tig. 160.' * P^ETEL, Couch. 



Sam., Ill, 1890, p. 144. 



Mexico. 



(Group of Lampsilis (/racilis.) 



Shell large, thin, elliptical or slightly obovate, with a high posterior 

 and an anterior wing, not greatly inflated; beaks low; epidermis rather 

 smooth, often feebly rayed, dull colored, but usually glossy; hinge line 

 slightly and rather regularly curved ; teeth compressed, pseadocardiuals 

 but feebly and often imperfectly developed; nacre purplish tinted, 

 rather dull. Shell of the male and female nearly alike, the latter 

 scarcely swollen at post basal region. Animal with the mantle greatly 

 thickened at posterior end, and double and thickened at post base, 

 where it is often crenulate or toothed on its inner border, and has the 

 outer developed into a flap; inner gill united to the abdominal sac 

 throughout; marsupium enormous, composed of a great number of 

 delicate semiradiatiug ovisacs, projecting far below the inner gills in a 

 semicircle. 



fLAMPSILIS GRACILIS Barnes. 



* Unio gracilis BARNES, Am. Jl. Sci., VI, 1823, p. 274.* HILDRETH, Am. Jl. Sci., 



XIV, 1828, p. 288. * DESHAYES, An. sans Vert, 2d ed., VI, 1835, p. 559; 3d 

 ed., II, 1839, p. 676; Tr. Element. Couch, 1839, p. 18, pi. xxx, figs. 2, 3. 

 *HANLEY, Test. Moll., 1842., p. 174. *C. B. ADAMS, Thompson's Hist. Ver- 

 mont, 1842, p. 166; * F. W. and L. Shells of Vermont, 1842, p. 16." HANLEY, 

 Biv. Shells, 1843, p. 174, pi. xx, tig. 37. * CATLOW and REEVE, Conch. Nom., 

 1845, p. 59.* DESHAYES, Tr. Klern., II, 1853, p. 217, pi. xxx, tigs. 2, 3.' H. 

 and A. ADAMS, Gen. Rec. Moll., II, 1857, p. 498. * SOWEKBY, Conch. Icon., 

 XVI, 1866, pi. xxxix, fig. 215.* CALKINS, Pr. Ottawa Ac. Sci., 1874, p. 42. 

 *LATCHFORD, Tr. Ottawa F. Nat. Club., 1882, p. 52. * B. H. WRIGHT, 

 Check List, 1888. 

 *Mya gracilis EATON, Zool. Text Book, 1826, p. 222. 



* Symphynota gracilis LEA, Tr. Am. Phil. Soc., Ill, 1830, p. 452. SHORT and 



EATON, Transylvania Jl., 1831, p. 80. * LEA, Obs., I, 1834, p. 66. 

 "Margarita (Unio) gracilis LEA, Syn., 1836, p. 11; 1838, p. 13. 



* Metaptera gracilis STIMPSON, Shells of N. Eng., 1851, p. 14. 



* Margaron (Unio) gracilix LEA, Syn. 1852, p. 19; 1870, p. 28. 



* 1 Anodon gracilis SOWERBY, Genera, No. XVII, 1823, tig. 



* Lampsilis gracilis BAKER, Moll. Chicago, Pt. 1, 1898, p. 99, pi. xix, fig. 1. 



* Uniofragilitt SWAINSON, Zool. 111., 1st ser., Ill, pi. CLXXI, 1823.- * DESHAYES, 



Encyc. Meth., II, 1830, p. 587. * SAY, Am. Conch., VI, 1834. * CONRAD, New 

 F. W. Shells, 1834, p. 69; *Monog., VI, 1836, p. 55, pi. xxx. * CHEXU, Bib. 



1 The description of the plate is dated 1856, and in the contents it is credited to 

 Reeve, although the previous plates bear date of 1865, and those following 1866. 



-Swainson's Unio frugil'm was published about the same time as Barnes's yracilis, 

 and as it is impossible for me to say which has priority, I agree with Lea that it is 

 better to adopt Barnes's well-known name. 



