﻿I.AMPSII.IS 



115 



tendency to be doubly looped ; surface covered with rather 

 faint, irreernlar growth lines, pale yellowish or greenish-yellow, 

 marked with numerous, wide or narrow, broken rays ; left valve 

 with two rather stumpy, small pseudocardinals and two small, 

 lamellar laterals; right valve with one pseudocardinal. with 

 usually a very faint, compressed one above it, and one lateral ; 

 beak cavities shallow, witli a few dorsal scars; muscle scars 

 shallow, the posterior nearly circular ; nacre bluish, somewhat 

 iridescent behind, slightly thicker in front. The male shell is 

 nearly evenly long ovate, often ending behind in a slight, 

 narrow biangulation about midway up the shell; the female 

 shell is slightly pointed behind midway up and has a moderate, 

 rounded marsupial swelling, and is generally smaller than that 

 of the male. 



Length (male) 65, height 34, diam. 20 mm. 

 Length (female) 58, height 28, diam. 17 mm. 

 St. Lawrence drainage; west to southern Michigan; Ohio 

 River system ; Illinois and Wisconsin. 



Type locality, Ohio. 

 Unio iris Lea^ Tr. Am. Phil. Soc, IH, 1830, p 439, pi. xi, fig. 

 18 ; Obs.. L 1834, p. 53, pi. XI, fig. 18.— HANI.EY, Biv. Shells, 

 1843, P- 206, pi. XXI, fig. 37.— Chenu, 111. Conch., 1858, pi. 

 VIII, figs, 7, ya, 76.— Reeve, Conch. Icon., XVI, 1865, pi. 

 XXIX, fig. 148. 

 Margarita (Unio) iris Lea, Syn., 1836, p. 2,7; 1838, p. 25. 

 Margaron (Unio) iris Lea, Syn., 1852, p. 38; 1870, p. 60. 

 Lampsilis iris Baker, Moll. Chicago, Pt. i, 1898, p. 105, pi. 



XIII, fig. I ; pi. XIV, fig. 2. — Simpson, Syn., 1900, p. 552. 

 Burynia (Micromya) iris Ortma.nn, Ann. Car. Mus., VIIT, 



1912, p. 341, fig. 23. 

 Unio crepcrns Lea, Tr. Am. Phil. Soc, VI, 1838, p. 2,2>^ pl- x. 

 fig. 28; Obs., II, 1838, p. 33, pl. X, fig. 28.— Chenu, 111. 

 Conch., 1858, pl. XXIII, figs. 5, 5a, 5&. 

 Margarita (Unio) creperus Lea, Syn.. 1836, p. 28; 1838, p. 20. 

 Margaron (Unio) creperus Lea, Syn., 1852, p. 31 ; 1870, p. 48. 

 Unio cresserus Hanley, Test. Moll., 1842, p. 196. 



