﻿MliDIONlDUS 247 



Medionidus coNRADicus (Lea). 



Shell rather small, long elliptical, usually arcuate, especially 

 when fully adult, subinflated, subsolid, inequilateral, rounded 

 in frOnt, with a low, sometimes scarcely developed, posterior 

 ridge ending in a rounded point at the posterior base ; beaks 

 only slightly inflated, but little elevated, sculptured with fine, 

 irregidar corrugated ridges, which have a tendency to fall into 

 two loops ; posterior end, especially the dorsal slope, generally 

 more or less wrinkled, sometimes the anterior half of the shell 

 shows slight corrugation ; epidermis scarcely shining, tawny 

 to yellowish-green, with feeble. i:rcken, wavy darker rays, 

 which sometimes show a tendency to break into blotches or 

 arrow-head markings ; left valve with two stumpy pseudocard- 

 inals and two laterals ; right valve with one pseudocardinal 

 and one lateral ; anterior scars deep ; posterior scars shallow ; 

 beak cavities but slightly excavated ; nacre bluish to dirty flesh- 

 color. The male shell is generally considerably arcuate and 

 is often wider behind ; that of the female is a little produced 

 along the middle of the base, and this part of the shell is 

 sometimes faintly, radially grooved. It is considerably thick- 

 ened in front. 



Length (male) 55, height 25, diam. 16 mm. 



Length (female) 42, height 18, diam. 14 mm. 



Tennessee River drainage ; Cahawba River, Alabama, and 

 probably the entire Alabama River system. 



Type locality unknown. 

 Unio conrodicus Lua, Tr. Am. Phil. Soc, VL p. 63, pi. ix, fig. 



2^ ; Obs., I, 1834, p. 175, pi. IX, fig. 2^. — Hanley, Biv. Shells, 



1843, P- 176; pl- XXIII, 22. — KusTER, Conch. Cab., Unio, 



1861, p. 179, pl. Lvi, fig. 5. — SowERBY, Conch. Icon., XVI, 



1866, pl. ijv, p. 278. 

 Margarita (Unio) conradicns Lea, Syn., 1836, p. 13; 1838, 



p. 14. 

 Margaron (Unio) conradicns Lea, Syn., 1852, p. 21. 

 Medionidiis conradicns Simpson, Syn., 1900, p. 589. — Ort- 



MANN, Ann. Car. Mus., VIII, 1912, p. 335, fig. 22. 



