870 QUADRULA 
little sinuate in front of the posterior ridge; outline of dorsal 
slope generally curved, sometimes raised into an angle behind 
the ligament; surface somewhat concentrically sculptured ; epi- 
dermis dark reddish-brown, dull; pseudocardinals triangular, 
ragged; laterals curved; beak cavities moderately deep; mus- 
cle scars small; nacre whitish or pinkish. 
Length 54, height 40, diam. 29 mm. 
Length 70, height 47, diam. 32 mm. 
Length 47, height 41, diam. 34 mm. 
Western Louisiana; eastern Texas. 
Type locality, Village Creek, Hardin Co., and Sabine River, 
Nexas. 
Unio askewi Marsu, Nautilus, X, 1896, p. 91; X, 1897, pl. 1, 
figs.n2, 4. 
OQuadrula askew SIMPSON, Syn., 1900, p. 786. 
Exceedingly variable. It has a higher, sharper posterior 
ridge than beadleiana and is generally more distinctly rhom- 
boid. 
QuaADRULA LANANENSIS Frierson. 
“Shell quadrate to triangular, nearly equilateral, anterior 
margin rounded. Base round in front, nearly straight behind. 
Posterior oblique, biangular, slightly emarginate. Dorsum 
curved; smooth, nearly polished above, striate below and up- 
on posterior slope. Lines of growth distinct and ill-defined. 
Dark reddish-brown, sometimes a little olive, obscurely radiate. 
Beaks eroded. umbos low, somewhat inflated. Anterior um- 
bonal slope rounded. Jateral slope flattened. Posterior ridge 
angular near the beaks, becoming obsolete near the base. Lig- 
ament brown, smooth, medium sized. Shell of medium thick- 
ness, thinner behind. Teeth double in left valve, single in 
right. Laterals rather thin, nearly straight. Cardinals stumpy. 
Muscle scars well marked, generally separate, sometimes con- 
fluent. Pallial line distinct in front, less so behind. Cavity of 
shell dish-like; of the beaks deep and full. Sometimes the 
dorsal muscle scars are situated in the extreme end of the beak 
cavity, but generally upon the base of cardinal and dorsal 
