890 QUADRULA 
Group of Quadrula subrotunda. 
Shell solid, rounded, elliptical or ovate, with high beaks 
curved inward and forward over a distinct lunule; beak sculp- 
ture a few coarse ridges curved up behind; posterior ridge 
feebly developed; epidermis brownish or blackish and often 
painted with a few faint rays on the earlier shell, which are 
disposed to break into squarish spots; hinge and teeth strong ; 
secondary lateral in right valve well developed; beak cavities 
deep, compressed; muscle scars deep. Animal with all four 
gills used as a marsupium throughout, filled with pink ova; 
gills large, inner only slightly the larger, free the greater part 
of their length; anal opening crenulate or papillose. 
QUADRULA BURSA-PASTORIS (B. H. Wright). 
Shell irregularly ovate or subrhomboid, subcompressed to 
convex, solid, inequilateral; beaks apparently not very full 
or greatly elevated: posterior ridge rather low, usually widely 
and faintly double; ending near the base of the shell in a bian- 
gulation; anterior end rounded, sometimes truncated above; 
base line curved or straight in young or adult shells, often 
slightly sinused in front of the posterior ridge in old speci- 
mens; outline of dorsal slope curved, sometimes subangular 
behind the ligament; surface rough, having strong, irregular, 
growth lines; epidermis brownish, wrinkled, dull; pseudocar- 
dinals radially striate; laterals heavy, that of the right valve 
somewhat double; muscle scars large, impressed; beak cavities 
deep, compressed ; nacre dirty white to lead-colored, generally 
with large, greenish-yellow blotches, thinner behind. 
Length 110, height 77, diam. 42 mm. 
Length 92, height 67, diam. 33 mm. 
Clinch and Powell Rivers; Virginia and Tennessee. 
Type locality, Powell River, Va. 
Unio bursa-pastoris B. H. Wricut, Naut., 1896, p. 133, pl. mr. 
Ouadrula bursa-pastoris SIMPSON, Syn., T900, p. 79T. 
Close to O. kirtlandiana, but generally more elongated and 
having more lurid nacre. The pallial iine is nearer the edge of 
the shell than it is in kirtlandiana and the epidermis is more 
inclined to be tawny-brown. 
