﻿OBOVARIA. 289 



Unio granadensis Conrad, Pr. Ac. N. Sci. Phila., VII, 1855, 



p. 256. 



A small form of this has been found as far east as Escambia 

 County, Florida. The pseudocardinals are usually split up into 

 radial, nodulous lamellae and are quite different from those of 

 any North American Naiad I know of. 



Conrad says that his Unio granadensis is suboval, with the 

 disks somewhat flattened, with minute radiating lines extend- 

 ing- to the tips of the beaks. He also states that the nacre of 

 his species is purple. The description therefore fits Lamarck's 

 species perfectly, though I have never known the species to 

 come from so far west as the Rio Grande, Conrad's locality. 



Genus OBOVARIA Rafinesque. 18 19. 



Obovaria Rafinesque, J. de Phys. Chim. Hist. Nat., 1819, p. 



426. — Ortmann, Ann. Car. Mus., VIII, 191 2, p. 320. 



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

 front, thinner behind, with high beaks, which are sculptured 

 very faint, irregular, often broken and slightly nodulous 

 ridges, which show a tendency to fall into two loops, the pos- 

 terior often open behind ; epidermis dull, brownish, silky, or 

 cloth-like, 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 ; pseudo- 

 cardinals solid, stumpy; laterals short, club-shaped: anterior 

 and posterior cicatrices deep and distinct : nacre bluish-white 

 or purple. 



Animal having the gills very short, 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 posterior part. 



Type, Unio retitsa Lamarck. 



The genus Obovaria, as I have defined it. consists of a few 

 species belonging to the Mississippi and Gulf drainage. 

 The shells are short, rounded or elliptical, solid and inflated 



