598 UNIO 
Unio gibbosus Barnes, Am. jl. Sci., VI, 1823, p. 262, pl. x1, 
fig. 12.—HAn ey, Biv. Shells, 1843, p. 207, pl. xx, fig. 54.— 
Kuster, Conch. Cab. Unio, 1852, p. 28, pl. 1v, figs. 3, 4.— 
SoweERBy, Conch. Icon., XVI, 1868, pl. Lxxut, fig. 379.— 
BAKER, Moll. Chicago, 1808, p. 70, pl. xiv, figs. 3, 4; Xv, 
figs. I-4.—SIMPSON, Syn., 1900, p. 703. 
Margarita (Unio) gibbosus Lema, Syn., 1836, p. 38; 1838, p. 25. 
Margaron (Unio) gibbosus Lea, Syn., 1852, p. 38; 1870, p. 61. 
Mya gibbosa Eaton, Zool. Text-Book, 1826, p. 220. 
Elliptio gibbosus ORTMANN, Ann. Car. Mus., VIII, 1912, p. 
221. 
Unio mucronatus BARNES, Am. Jl. Sci., VI, 1823, p. 266, pl. 
Kilt, US Tse othe). 
Mya mucronata Eaton, Zool. Text-Book, 1826, p. 221. 
Unio dilatatus Say, Am. Conch., VI, 1834.—Conrap, Monog., 
V, 1836, p. 42, pl. xx1.—Kusrer, Conch. Cab. Unio, 1852, 
p. 38, pl. vi, fig. 4. 
Unio torulosus Frrussac, Guer. Mag., 1835, p. 28. 
Unio arctatus Ferussac, Guer. Mag., 1835, p. 29. 
Unio arctior Lea, Vr: Am, Phil. Soc, VI, 18385 p. 10; pli, 
fig. 10; Obs., II, 1838, p. 10, pl. iv, fig. 10 —HANLeEy, Biv. 
Shells. 1843, p. 208, pl. xxtr, fg. 46.—Kuster, Conch. Cab. 
Unio, 1861, p. 170, pl. Lvi, fig. 6 —CHENU, II]. Conch., 1858, 
pl. xxI, figs. 2, 2a, 2b.—?Sowersy, Conch. Icon., XVI, 1868, 
pls eK KV, hig 22: 
Margarita (Unio) arctior Lea, Syn., 1836, p. 39; 1838, p. 25. 
Margaron (Unio) arctior LEA, Syn., 1852, p. 38; 1870, p. 7I. 
A species having an immense distribution in no less than 
four distinct drainage systems and very abundant in individ- 
uals. Certain specimens superficially resemble specimens of 
Ptychobranchus phaseolus in form and the shape of the teeth, 
but the marsupia are very different in these species and the 
shells of gibbosus have different color pattern and duller col- 
ored nacre. Some of the variations of this species are probably 
worthy of names. 
