UNIO 7°7 
Unio camptodon Say, Am, Conch., V, 1832, pl. xi1.—Han- 
LEY, Biv. Shells, 1843, p. 198, pl. xxi, fig. 17—CHENU, Bib. 
(Conch ist. ser, Cll, 1645, p: 53, pl. Xiv, figs. 2, 2a, 2b— 
Sowersy, Conch. Icon., XVI, 1868, pl. Lxx, fig. 356. 
Margarita (Umo) camptodon Lea, Syn., 1836, p. 30; 1838, p. 
2K, 
Margaran (Unio) camptodon LEA, Syn., 1852, p. 32; 1870, p. 
50. 
Unio tetralasmus var. camptodon SIMPSON, Syn., 1900, p. 740. 
Unio geometricus Lea, Tr. Am. Phil. Soc., V, 1832, p. 38, pl. 
Iveco, o> Obs... F-18345 perso; pli 1v,. fig. 10: 
Unio decliwis geometricus FRtERSON, Naut., XVII, 1903, p. 49, 
pl. 111, middle fig. 
This form is decidedly obliquely truncated on the dorsal 
slope; the posterior ridge is rather high and rounded and ends 
at or near the base of the shell in a rounded point. Adult shells 
have the base line incurved medially and the anterior end is 
either evenly rounded or angled above. The surface is darker 
and usually rougher than it is in typical specimens. It is a 
little difficult to say just what Lea’s U. geometricus is, as the 
type does not seem to be in his collection. It is a young shell 
and is described as dark brown with a wrinkled and sometimes 
obscurely rayed epidermis. It seems from the figure to stand 
somewhat between Say’s camptodon and declivis, but I think 
that the form is nearer the latter, as the base line is almost 
straight. 
Var. manubius Gould. 
Shell often becoming large; dorsal and ventral lines more or 
less curved, somewhat rhomboid, the dorsal slope being more 
or less obliquely truncated; surface yellowish-ashy, dull or 
feebly shining. 
Length 102, height 55, diam. 33 mm. 
Length 131, height 68, diam. 41 mm. 
Type locality, Chihuahua, sixty miles from Fort Ringgold. 
Unio manubtus Goutp, Pr. Bost. Soc. Nat. Hist., V, 1856, p. 
220. 
Margaron (Unio) manubius Lea, Syn., 1870, p. 54. 
Unio manubrius Payrer, Conch. Sam., III, 1890, p. 158. 
