QUADRULA 863 
ly smooth; the posterior slope shows faint plications in some 
individuals and there are rarely traces of pustules on the disk ; 
epidermis greenish-yellow or yellowish-green, somewhat cloth- 
like when fresh; pseudocardinals considerably split up; lateral 
of the right valve single or partly double; beak cavities moder- 
ately deep, compressed; muscle scars small; nacre dirty whit- 
ish. 
Length 30, height 23, diam. 15 mm. 
Lexas: 
Type locality, Columbus, Miss. 
Unio pauperculus Lea, Pr. Ac. N. Sci. Phila., V, 1861, p. 39; 
ieNce Ne sete hia. Vi 1862, p.90, pl xv, fe. 247; Obs:, 
WIE 1662) p. 102, pl. xv, fis. 247. 
Margaron (Unio) pauperculus Lea, Syn., 1870, p. 55. 
Ouadrula paupercula SIMPSON, Syn., 1900, p. 783. 
The above measurements are from the type. I have seen a 
specimen in the collection of Wm. A. Marsh, Sr., which is 
somewhat larger and has a few faint tubercles on the disk. It 
is a doubtful species, and all the material I have seen is prob- 
ably young. I,ea’s shell and a couple of others I have seen 
have been scraped until the epidermis has been nearly de- 
stroyed. The color and the angular posterior ridge differ from 
those in any closely allied form, yet it may be the young of 
some well-known species. 
Group of Quadrula infucata. 
Shell small, rounded rhomboid, with a low, distinct posterior 
ridge, truncated behind and angled back of the ligament ; beaks 
moderately elevated, subcentral; beak sculpture, four or five 
coarse, subparallel ridges, which curve upward behind, with 
fine, radial ridges between them and the ligament; surface 
blackish, sculptured with zigzag or chevron-shaped corruga- 
tions, which often become pustulous below; posterior slope 
having radial, broken wrinkles ; pseudocardinals small, stumpy ; 
secondary lateral of the right valve present ; beak cavities mod- 
erately deep, slightly compressed ; anterior scars small, smooth ; 
nacre rather dull, purplish. 
