140 THE AMERICAN MIDLAND NATURALIST 
by rather coarse, irregular ridges, extending as tubercles on the 
disk; epidermis yellowish green with alternate bands of brown and 
straw color. Interior of shell much like adult except not so broad, 
nor as upright, nor as long; nacre white with light blue irridescent 
sheen posteriorly. 
MISCELLANEOUS REMARKS:—Q. nodulata seems to be only a 
globular-shaped Q. quadrula and is more typically a southern 
shell; however, it is occasionally met with in the Upper Mississ- 
ippi, where it is most found in this State. Mr. B. F. Bush col- 
lected some miscellaneous shells from the interior of the state 
and donated them to the United States Museum where some 
were identified as this species. It is to be distinguished from Q. 
pustulosa especially by two regular radiating rows of widely 
separated tubercles obliquely arranged from the umbones to the 
ventral margin on the posterior half of the disk; then, too, it is 
more inflated, is not so upright, has greater umboidal ratio, has 
more of an alated dorsal ridge and belongs to the so-called ‘‘ Lach- 
rymosa’’ Group, whereas, pustulosa is a member of the first group 
of this Genus of which it is the type; hence, the latter is, after 
all, not even closely allied. However, there is not much difference 
between these two Quadrulae as to the form and size of their 
larvae, and as to form of adult shell, it lies nearer to the variety, 
contraryensts of Q. quadrula. Surber (1913, p. 113) finds this 
species to be a gill parasite upon the crappie (Pomoxis annularts) 
as an occasional host. As to its breeding habit, it is tachytictic. 
Quadrula fragosa (Conrad). 
(‘Hickory Nut Shell.’’) 
Pl. XVIII, Figs. 48 A and B. 
1836— Unio fragosus Conrad, Monog. of Fresh-water Shells, II, p. 12, 
Pl Wolters, 2), 
ANIMAL CHARACTERS. 
NUTRITIVE AND REPRODUCTIVE STRUCTURES :—Identical with 
Q. quadrula as far as can be determined, with the scanty supply 
of material at hand—none of which is in gravid condition. How- 
ever, Wilson and Clark (1914, pp. 59 and 60) report it with all 
four gills marsupial, thick, pad-like. Glochidium unknown. 
SHELL CHARACTERS. 
EXTERNAL STRUCTURES:—Shell most quadrate of the Quad- 
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