590 ONIO 
rubbed; left valve with two stumpy pseudocardinals and two 
laterals, the upper smaller; right valve with one ragged pseu- 
docardinal and one, often partly double, lateral; muscle scars 
impressed, the anterior ones rough; beak cavities shallow, 
showing numerous dorsal scars; nacre purple or coppery. 
Length 55, height 35, diam. 24 mm. 
Length 48, height 30, diam. 25 mm. 
Mexico, in the vicinity of Vera Cruz. 
Margarita (Unio) carbonarius LEA, Syn., 1836, p. 192; 1838, 
Dalz 
Unio carbonarius Lea, Tr. Am. Phil. Soc., VI, 1838, p. 37, pl. 
*1, fig. 32; Obs., II, 1838, p. 37, pl. x1, fig? 32.— HANEY, 
Biv. Shells, 1843, p. 184, pl. xxu, fig. 10—CuHENu, IIl. 
Conch:, 1858, pl. xxi, figs. 1, 1a, 10. 
Margarita (Unio) pliciferus Lea, Syn., 1836, p. 13; 1838, p. 
TA: 
Unio pliciferus Lea, Tr. Am. Phil. Soc., V, 1838, p. 61, pl. 
XVI, nig. 535 Obs. 1, 1838, p60, pl xvi fees setae 
LEY, Biv. Shells, 1843, p. 176, pl..xx, fig. 32-—KUSTER, 
Conch. Cab., 1848, p. 142, pl. xu, fig. 1—CuHeENu, Ill. 
Conch., 1858, pl. xxi, figs. 5, 5a, 5b; Manual, 1859, II, p. 
142, fig. 702.—Sowersy, Conch. Icon., XVI, 1868, pl. Lxxv, 
fig. 387.—FiscHER and Crossk, Miss. Sci. I, 1894, p. 580. 
pl LXV, ns) 2 exe figs) 2: 2a: 
Margaron (Unio) pliciferus L&A, Syn., 1852, p. 20; 1870, p. 31. 
Unio plexus Conrap, Monog., X, 1838, p. 89, pl. xLix, figs. 
1, 2.— SIMPSON, Syn., 1900, p. 701. 
Var. minor Fischer and Crosse. 
Shell considerably smaller than the type, the epidermis in 
the specimens examined brownish and shining. 
Length 35, height 20, diam. 14 mm. 
Habitat with the typical form in East Mexico. 
Unio pliciferus var. minor, Fisctter and Crossr, Miss. Sci. I, 
1834, p. 580, pl. LXrx, fig. 4—von Martens, Biol. Cent. Am., 
Moll., 1900, p. 515, pl. XXxX1X, figs. 4, 4a. 
