88 THE CHICAGO ACADEMY OF SCIENCES. 
without papillz; branchial large with small blackish papille; 
mantle yellowish brown, approaching to salmon, edged with 
black; liver and cardiac pouch brownish; heart with very 
regular pulsations, numbering twenty-three per minute. Four 
gills used as marsupia. 
Distribution: Ohio and North Carolina west to Kansas and 
Iowa, Wisconsin south to Louisiana and Texas. 
Geological distribution: Pleistocene. 
Habitat: Found in the larger rivers and lakes, on a muddy 
bottom. 
Remarks: This is one of the most variable of North 
American Unios, and has received a large number of names, as 
the synonymy onthe previous page shows. The shell varies 
from entirely smooth or with few pustules (schoolcraftii) toa con- 
dition where the whole valve is covered with pustules, and the 
pustules may be long and narrow or round. The umbones vary 
from depressed to elevated and the cardinal] teeth show a dozen 
or fifteen different modifications. The writer has before him at 
the present time nineteen different varieties of this shell, from a 
number of States. It is acommon and widely diffused species, 
and with all its mutation, is easily recognized when once known. 
It is quite common in the southern region, in Calumet Lake and 
River, and is also found in the Desplaines River, near Joliet. 
Ovisacs distinct, occupying a part of outer branchiz of 
females. (Simpson.) 
Genus OBLIQUARIA (Rafinesque) Simpson, 1898. 
Shell: Solid, inflated, oval in outline, obliquely truncated 
and pointed behind with a well developed posterior ridge; beaks 
prominent, sculptured with a few strong ridges which are heay- 
iest where they cross the posterior ridge; posterior slope and 
sometimes the entire shell covered with wavy or chevron shaped 
folds; a row of three or four strong elevated nodules, com- 
pressed lengthwise, extends from the beaks down the center of 
the shell and the region behind this is somewhat excavated; 
epidermis bright and smooth, sometimes a little wrinkled, a 
uniform yellowish brown or painted with delicate broken green 
lines which often become zigzagged; left valve with two heavy 
pseudo-cardinals and two laterals, right valve with one strong 
pseudo-cardinal, with often a smaller one in front and behind it, 
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