NO. 1205. SYNOPSIS OF THE NAIADES— SIMPSON. 599 



Genus OBOVARIA Rafinesque, 1819. 

 (Type, Unio retusa Lamarck.) 

 Oioraria Rafinesque, J. de Phys. Chim. Hist. Nat., 1819, p. 426.' 



Shell short, oval, rounded, or retuse, solid, inflated, thick in front, 

 thinner behind, with high beaks which are sculptured with very faint, 

 irregular, often broken and slightly nodulous ridges which show a ten- 

 dency to fall into two loops, the posterior often open behind ; epidermis 

 dull, brownish, silky or clothlike, rarely rayed, rays indistinct; female 

 shell but slightly inflated in the post-basal region, commonly having a 

 shallow furrow or a flattened area at the posterior end; pseudocardinals 

 solid, stumpy; laterals short, club-shaped; anterior and posterior cica- 

 trices deep and distinct; nacre bluish white or purple. 



Animal with very short gills, the inner united to the abdominal sac 

 throughout; marsupium projecting far below the rest of the branchiae 

 and occupying the posterior portion of the outer gills, dolabriform 

 or kidney shaped; mantle with a wide, thickened double-edged border, 

 the inner edge of which is often slightly toothed at its postbasal part. 



Subgenus OBOVARIA Rafinesque, 1819. 

 (Type, Unio retusa Lamarck.) 



Shell retrose to short oval; beaks high, central; pseudocardinals 

 rarely parallel with the laterals; cavity of the beaks deep, subcom- 

 pressed; nacre bluish white or purple. Animal with the characters 

 of the genus. 



t OBOVARIA RETUSA Lamarck. 



* Unio retusa Lamarck, An. sans Vert., VI, 1819, p. 72. — Ferussac, Guer. Mag,, 



1835, p. 28.— Deshayes, An. sans Vert., 2d ed., VI, 1835, p. 534 ; 3d ed., II, 1839, 

 p. 668. 



""Unio retusus Conkad, Monog., II, 1836, p. 19, pl.viii.—* Reeve, Conch. Sy8t.,I, 

 1841, p. 118, pi. Lxxxviii, fig. 16.— *Hanley, Test. Moll., 1842, p. 202; *Biv. 

 Shells, 1843, p. 202, pi. xxi, fig. 11.— *Catlow and Reeve, Conch. Nom., 1845, 

 p. 63.—* KusTER Conch. Icon. Cab. Unio, 1852, p. 58, pi. xiii, fig. 2.—* Conrad, 

 Pr. Ac. N. Sci. Phila., VI, 1853, p. 256.—* Sowerby, Conch. Icon., XVI, 1868, 

 pi. Lxxi, fig. 363.— * Calkins, Pr. Ottawa Ac. Sci., 1874, p. 44.— *B. H. 

 Wright, Check List, 1888.— *PiETEL, Conch. Sam., Ill, 1890, p. 165.— * Call, 

 Tr. Acad. Sci. St. Louis, VII, 1895, p. 45, pi. viii. 



^Margarita ( Unio) retusus Lea, Syn., 1836, p. 34 ; 1838, p. 23. 



*Margaron ( Unio) retusus Lea, Syn., 1852, p. 35; 1870, p. 56. 



* Unio torsus Potiez and Michald, Gall. Moll., 1844, p. 149, pi. LVii, tigs. 1, 2. 



Ohio, Cumberland, and Tennessee river systems. 



1 1 am utterly unable to guess as to what Rafinesque's first species ( Obovaria oio- 

 valis) is, and the second (0. torsa) is either the Unio retusa of Lamarck or a variety 

 of Lea's U. circulus with purple nacre, I can not be certain which.- Which of these 

 two nearly related species it may be, I consider it sufiicient to establish the genus, 

 his description being applicable. 



