892 QUADRULA 
The young shell is very different from that of bursapastoris, 
being short, and quadrate or elliptical, smooth and rayed, 
while that of the latter is long oval, and scarcely rayed. Q. 
kirtlandiana is not as elongated as bursapastoris and is usually 
curved on the base line. 
Var. minor Simpson. 
Shell smaller and more delicate in every way than the type, 
not very solid, usually greenish-yellow or greenish-brown, the 
young with broken rays. 
Length 63, height 48, diam. 22 mm. 
Length 40, height 37, diam. 20 mm. 
Type locality, Various localities in the ‘Tennessee River 
drainage. 
Quadrula kirtlandiana var. minor SIMPSON, Syn., 1900, p. 791. 
It was the opinion of the late Prof. A. G. Wetherby that this 
is a form of Lea’s Unio subrotundus. It seems to me to be 
too much compressed for that species, which is generally quite 
inflated. Dr. Sterki believes that O. swbrotunda and kirtland- 
zana should be united. ‘While they approach closely and there 
may be intermediates that can scarcely be named, it seems to 
me they are as distinct as most of the closely related species 
of this and other allied groups. 
QUADRULA SUBROTUNDA (Lea). 
Shell irregularly elliptical or subquadrate in outline, subin- 
flated to inflated, solid, inequilateral; beaks high, full, turned 
forward over a lunule, their sculpture a few subnodular ridges 
or wrinkles; anterior end obliquely truncate above, rounded 
below; base line curved throughout, sometimes quite full 
behind the middle of the shell; outline of dorsal slope curved, 
raised almost to an angle behind the ligament; surface gener- 
ally sculptured with low, wide, concentric ridges; epidermis 
greenish-brown, somewhat cloth-like, usually with wide and 
narrow green, broken rays in the young, which often remain 
on the umbonal region in the adult shell; pseudocardinals tri- 
angular, rough; lateral in the right valve disposed to be double ; 
