QUADRULA 825 
Margaron (Unio) boykimanus Lea, Syn., 1852, p. 19; 1870, 
p. 28. 
Plectomerus boykinianus Conrap, Pr. Ac. N. Sci. Phila., VI, 
1853, p. 260. 
Quadrula boykiniana SIMPSON, Syn., 1900, p. 770. 
Unto baykinianus Pairer, Conch. Sam., III, 1890, p. 145. 
Differs from Q. triwmphans in being longer in proportion 
to its height, in being less rounded and in having chevron- 
shaped sculpture. But it is quite probable that the two will be 
found to run together, when a sufficient amount of material 
is examined. 
QUADRULA HEROS (Say). 
Shell long rhomboid or long quardate, subintlated to inflated, 
solid, inequilateral ; posterior ridge usually full, rounded ; beaks 
rather full and high, their sculpture strong, doubly looped or 
zigzag ridges; dorsal line straight or lightly curved; anterior 
end rounded, generally angled above; base line straight or a 
little curved; posterior end almost squarely or somewhat 
obliquely truncate and angled above where it joins the low 
dorsal wing, rounded below; surface with uneven,. concentric 
sculpture, all, except the anterior basal part, more or less 
covered with oblique folds and nodules. The earlier growth 
is usually densely covered with subradial or chevron-shaped, 
nodulous plications; frequently the sculpture in front is de- 
cidedly nodulous: epidermis brownish or blackish; pseudo- 
cardinals elevated, radial, radially striate; laterals straight or 
slightly curved; muscle scars large, the anterior ones with 
rough nacreous matter; beak cavities deep, compressed ; nacre 
whitish, often blotched with lurid color, much thinner and irt- 
descent behind; pallial line remote. 
Length 210, height 133, diam. 70 mm. 
Length 133, height 91, diam. 60 mm. 
Length 112, height 82, diam. 55 mm. 
Mississippi River system generally ; Red River of the North; 
Tombigbee River, Alabama; southwest to New Leon, Mexico. 
Type locality, Fox River, tributary of the Wabash. 
