546 UNIO 
a tendency to break into nodules; anterior end decidedly trun- 
cate and angled above in old shells, more nearly rounded in 
young ones; posterior ridge close to the dorsal line, ending 
behind in a point above the median line ; post-basal part of the 
shell a little produced; surface almost smooth, having feeble 
growth lines; epidermis yellowish, greenish-yellow, tawny or 
brownish, usually showing the rest periods; left valve with 
two compressed, often united, pseudocardinals and two curved, 
lamellar laterals, the upper small; right valve with a single 
compressed pseudocardinal and one lateral; pseudocardinals 
somewhat reflexed; beak cavities moderately deep; nacre 
white, silvery, thicker in front; anterior scars very deep; pos- 
terior scars shallow. 
Length 92, height 47, diam. 37 mm. 
Asia Minor; Assyria. 
Unio truncatus Swainson, Zool. Hl., 2d ser., I, 1829, pl. x.— 
SOWERBY, Conch. Icon., XVI, 1868, pl. LX xxv, fig. 453. 
Margarita (Unio) truncatus LEA, Syn., 1836, p. 21; 1838, p. 18. 
Margaron (Unio) truncatus Lea, Syn., 1852, p. 26; 1870, p. 39. 
Unio tigridis Bourcuicnat, Test. Nov. Saul., 1852, p. 30; Cat. 
Rais. Moll., 1853, p. 77, pl. iv, figs. 7-9.—Kustrer, Conch. 
Cab. Unio, 1861, p. 227, pl. Lxxvu, fig. 1—Kose.r, Icon., 
new ser., I], 1886, p. 2, pl. Xxxu, fig. 226.—SimPpsoN, Syn., 
1900, p. 688.—Koset, fcon., new ed., XVIII, 1912, p. 62, 
pl. DX, figs. 2683, 2684. 
Umo disnatus. Lea, Pr. Ac: N. Scu Phila., VII, 1863; po 180; 
JietAcadIN.;Sei:. Phila., Wi 2866," ps si, plexyueiee or 
Obs., XI, 1867, p. 55, pl. xvi, fig. 48—Kose.t, Icon., new 
ed., XVIII, 1912, p.. 43, pl. pm, fig. 2654. 
Margaron (Unio) dignatus Lea, Syn., 1870, p. 39. 
Unio dignatus semiramidis Koper, Icon., new ed., XIX, 1912, 
p. 11, pl. pxvit, fig. 2698. 
Unio dignatus assuricus Korg, Icon., new ed., XIX, 1912, 
p. 13, pl. Dxvitt, fig. 2690. 
Unio dignatus ninusi Korver, Icon., new ed., XIX, 1912, p. 
13, pl. pxviit, fig. 2700. 
Margaron (Unio) tigris Lea, Syn., 1870, p. 39. 
