538 UNIO 
above it, and one lateral ; beak cavities moderately deep; nacre 
whitish or bluish-white, not’brilliant, thickened a little in front. 
Length 113, height 52, diam. 39 mm. 
Length 77, height 40, diam. 25 mm. 
Northern and middle Europe; eastern Siberia. 
Unio tumidus Rerzrus, Diss. Hist. Nat., 1778, p. 17,—Ross- 
MASSLER, Icon., I, 1835, p. 117; pl. Mm fisse 70, 70a, 70mm Uk 
1836, p. 27, pl. xiv, figs. 202-2043 VATE I638ep ey pleet 
fig. 543; XII, 1844, p. 32, pl. Lx, figs. 772-778.—Brown, L. 
and F. W. Conch., 1836, p. 109, pl. xx1, figs. 8, 9 —Brown, 
Ill. Rec. Conch., 1844, p. 82, pl. xxxm, figs. 5-8.—STABILE, 
Faun. Lug., 1845, p. 61, pl. 11, fig. 74.—Dupuy, Hist. Moll. 
Fr., 1852, p. 655, pl. xxvi, fig. 20—Forses and HANLEY, 
Hist. Brit. Moll., I], 1853, p. 140, pl. x1, fig. 1.—KUSTER, 
Conch. Cab. Unio, 1854, p. 71, pls. xvi, xvi1.—MoguIn- 
Tanpon, Moll. Terr. Fluv., II, 1855, p. 577, pl. 11, figs. 11, 
14.—NORDENSKIOILD and NYLANDER, Fin. Moll., 1856, p. 85, 
pl. v1, figs. 7, 8—Drouet, Nay. Fr., II, 1857, p. 110, pl. rx, 
fig. 2—Sowerpy, Ill. Int. British Shells, 1859, pl. vi1, No. 3- 
—Rereve, L. and F. W. Moll. Brit., 1863, p. 210, fig. 1.— 
Reeve, Conch. Icon., XVI, 1865, pl. xxv, fig. 124.—TarTE, 
L. and F. W. Moll. Brit., 1866, pl. 11, fig. 2—Ct1xssin, Deuts. 
Bx. Moll., 1876, p. 458, fig. 299.—L. Anams, Coll. Man., 
1884, p. 18, pl. L, fig. 1o—Koserwt, Icon., new ed., VI, 1893, 
p. 87, pl. cLxxul, fig. 1115.—S1mpson, Syn., 1900, p. 684. 
Margaron (Unio) tumidus Lua, Syn., 1852, p. 36; 1870, p. 58. 
Unio tumida C. Prreirrer, Nat. Deuts. L. and S. Moll., I, 
1925, p: 34, pl. vu, figs. 2, 33 pl vit, nese 
Mya depressa Donovan, Brit. Shells, ITI, 1801, pl. cr.— 
CHenv, Bib. Conch.; 1st Ser. 1, 1645p ie pln sex sess 
1-3. 
Unio depressus Paret,, Conch. Sam., IIT, 1890, p. 150. 
Mya ovata Donovan, Brit. Shells, IV, 1802, pl. cxx11.—Woop, 
Gen. Conch., I, 1815, p. tos, pl. xrx, fig. 5; Ind. Test., 1825, 
p. 12, pla, fig 27c. rev. ed., 1856, py aio pln mene eye 
CuEnu, Bib. Conch., 1st Ser., I, 1845, p. 82, pl. xxxu1, figs. 
1-3. 
