142 THE AMERICAN MIDLAND NATURALIST 
‘inner laminae of inner gills free from visceral mass; palpi long and 
broad; soft parts a light tan. 
REPRODUCTIVE STRUCTURES:—Marsupia identical with those 
of Q. quadrula. No gravid forms found. 
SHELL CHARACTERS. 
‘ 
EXTERNAL STRUCTURES:—Shell small, subquadrate, biangu- 
lated behind, the biangulation pointed ventrad; post-dorsal ridge 
costated; post-umbonal ridge prominent, profusely tubercled; 
radial furrow rather wide and shallow, bounded in front by a rather 
scattered row of sharp tubercles; epidermis blackish. 
INTERNAL STRUCTURES :—lIdentical with those of Q. nobilis 
which are somewhat peculiar. 
Sex Length Height Diameter Locality 
O52.) Xan AG) Sen 2onim (Osage R., Warsaw, Mo.) 
Thine S', Be es BOs Se dyer Ne eee « Ad yee) 
OM RAO) XIN 28 Roe! (he as rad aD 
MISCELLANEOUS REMARKS.—Although this species has only 
been found in the Osage basin for this State, yet it is not to say, 
a very common shell there. So closely related is this small form 
of quadrula to Q. nobilis that a good series of shells may reveal it 
as the young of nobilis. Aspera has been considered the southern 
form of Q. quadrula and it may be the small multi-tuberculated 
representative of the South-west which is connected geographically 
by all forms of intergrades to that large, heavy, smoother repre- 
sentative of the North Mississippi Valley. 
Quadrula nobilis (Conrad). 
(“Big Buck Horn,’ “Maple Leaf.’’) 
Pl ie RX Rags. ve ECA ate ibe 
1854—Unio nobilis Conrad. yi: Acad... Nat. Sei. Phila., IL, px/297% 
P]. X XVII, figs. 2 and 3. 
ANIMAL CHARACTERS. 
NUTRITIVE STRUCTURES:—Branchial opening large with 
feathered papillae, anal crenulated, supra-anal without mantle- 
connection to anal—hence both openings virtually one, gills 
long, rather narrow, inner laminae of inner free only one-half 
way, palpi enormous connected two-thirds of their length antero- 
