824 QUADRULA 
In some characters this species is close to O. boykiniana. 
‘The general sculpture is much as it is in that species, but in the 
type, the only absolutely authentic specimen I have seen, there 
is no indication of chevron shaped patterns. I have seen ma- 
terial, which hints strongly at a connection of the two species 
and would not be surprised if it would eventually be found 
necessary to unite them, different as they are typically. 
(QUADRUI,A BOYKINIANA (Lea). 
Shell trapezoid or subrhomboid, subinflated to inflated, solid, 
inequilateral ; beaks full and elevated, their sculpture consist- 
ing of coarse, sometimes doubly looped or zigzagged, nodu- 
lous ridges; anterior end narrowed and rounded, often full 
and subangular above and slightly cut away below; base line 
straight or nearly so; post-dorsal part produced into a rather 
high wing; posterior end almost squarely or obliquely trun- 
cate, rounded or pointed below the median line; posterior ridge 
moderate to full, rounded; surface with strong, irregular con- 
centric sculpture and covered with oblique, corrugated or sub- 
nodulous plications. These folds are generally strongest along 
the posterior portion, where they are often divaricate and they 
frequently are formed into irregular, chevron-shaped patterns 
on the anterior half of the shell; epidermis dark brown or 
blackish; pseudocardinals radially striate, often uneven and 
broken up; laterals granular; beak cavities deep, compressed : 
posterior scars indistinct; anterior scars nearly filled with 
rough nacre; nacre white, often dull purplish in the cavities, 
much thinner and iridescent behind. 
Length 162, height too, diam. 63 mm. 
Length 112, height 86, diam. 43 mm. 
Chattahoochee River system: Claiborne, Alabama; Pine 
Barren Creek, Escambia County, Florida. 
Type locality, Chattahoochee River, Columbus, Ga. 
Unio boykinianus Lea, Pr. Am. Phil. Soc., I, 1840, p. 288; 
Tr. Am., Phil, Soc:, VEL, 1842) ps 208 spl saiias 222s 
Obs., III, 1842, p. 46, pl. x11, fig. 22—CueEnu, Ill. Conch., 
188, pl. xxvit, figs. 2, 2a, 2b—Kuster, Conch. Cab., 1861, 
p. 181, pl. tvi, fig. 1—Sowexrey, Conch. Icon., XVI. 1868, 
pli fiesta 
