NO. 1205. SYNOPSIS OF THE NAIADES SlMTsoy. 589 



portion of the shell plicately or nodulously wrinkled; epidermis smooth 

 and bright, variegated with broken green rays and blotches; beak sculp- 

 ture consisting of rather fine, subparallel, often broken ridges in two 

 loops, the anterior rounded, the posterior somewhat angled, occasion- 

 ally broken up into zigzags; l pseudocardiuals small, stumpy and some- 

 what roughened; laterals rather short, slightly curved and club-shaped, 

 remote; dorsal cicatrices few, placed under the hinge just behind the 

 beaks; anterior cicatrices rather deep; posterior cicatrices rounded, 

 large, and well impressed; anterior part of shell somewhat thickened; 

 female shell slightly swollen just behind the middle of the base. 



Animal with the inner gills wholly or in part free from the abdominal 

 sac; marsupium occupying the central posterior part of the outer gills, 

 sometimes extending nearly their whole length, consisting of few to 

 many rather large, irregular ovisacs, which are not so distinctly 

 marked out as in Lampsilis, but which have rounded bases; mantle 

 much thickened on its lower edge, which is dark colored and sometimes 

 papillous. 



(Group of Medionidus conradicus.} 



Shell small, usually with a well-denned posterior ridge; posterior end 

 and sometimes the greater part, of the shell slightly wrinkled or nodu- 

 lous; epidermis rather smooth, painted with rays broken into irregular 

 arrow-head markings or blotches; pseudocardinals rather small and 

 imperfectly developed; laterals of left valve separated by a narrow, 

 shallow furrow; nacre greenish, purplish, or bluish. The male shell is 

 often decidedly arcuate; that of the female is swollen at or behind the 

 center of the base. Animal having the characters of the genus. 



t MEDIONIDUS CONRADICUS Lea. 



* Vnio conradicus LEA, Tr. Am. Phil. Soc., VI, 1834, p. 63, pi. ix, fig. 23; *Obs., I, 



1834, p. 175, pi. ix, fig. 23. * FERUSSAC, Guerin. Mag., 1835, p. 29. '* HANLEY, 

 Test. Moll., 1842, p. 176; * Biv. Shells, 1843, p. 176, pi. xxm, fig. 22.* CATLOW 

 and REEVE, Conch. Noui., 1845, p. 57. * CONRAD, Pr. Ac. N. Sci. Phila., VI, 

 1853, p. 247.' H. and A. ADAMS, Gen. Rec. Moll., II, 1857, p. 497. *KuSTER, 

 Conch. Cab. Unio, 1861, p. 179, pi. LVI, fig. 5. * SOWERBY, Conch. Icon., 

 XVI, 1866, pi. nv, fig. 278. * P/ETEL, Conch. Sam., Ill, 1890, p. 148. 



* Margarita ( Unio) conradicus LEA, Syn., 1836, p. 13; 1838, p. 14. 

 MargttroH ( L'nio) conradicus LEA, Syn., 1852, p. 21. 



I'nio conradius CONRAD, Monog., X, 1838, p. 87, pi. XLVII, fig. 3. 



* .}faryaron ( I'nio) con radian us LEA, Syn., 1870, p. 32. 



* I'nio conradiamis B. H. WRIGHT, Check List. 1888. 



Tennessee Eiver drainage; Cahawba River, Alabama, and probably 

 the entire Alabama Kiver system. 



'The beaks in all the specimens of Fnio sitbtenlus that I have examined were too 

 badly eroded to make out the character of the sculpture with certainty. In a gen- 

 eral way they seemed to be much like those of the C'onradicus group, only coarser. 



