184 — THE AMERICAN MIDLAND NATURALIST 
_SHELL CHARACTERS. 
EXTERNAL STRUCTURES:—Shell orbicular, to egg-shape in 
general outline, disk tuberculated and transversely nodulous 
between beaks and ventral margin in front of post-umbonal ridge; 
latter flattened, dorsal ridge low, faintly costated; beaks low, 
well placed anteriorly; epidermis light-brown to yellowish, some- 
what glossy. 
INTERNAL STRUCTURES:—Cardinals tripartite in left valve, 
rather single in right; interdentum broad, rather doubly gashed 
in right valve; laterals double in left and single in right valve; 
mantle line high up from ventral margin; nacre whitish, pinkish 
(or even bluish) within the mantle line, usually lighter color on 
extra-mantle line border. 
Sex Length Height Diameter Locality 
SOOM UXee ESSN Ree 32 (Gasconade R., Gascondy) 
OF 7-75 UXO De weXe MAUL (Osage R., Monegaw Springs) 
Ce 7Oumaxe OAN EX AO eee ” Warsaw) 
MISCELLANEOUS REMARKS:—As this state is out of geographic 
range of typical cooperianus it is natural that no real type may be 
found in Missouri. However, the writer upon finding a few shells 
of the tuberculata (Raf.) type with white and pink nacre submitted 
one of the latter to Mr. Walker for his consideration. His com- 
ments are:—‘‘A very curious and interesting shell. It has the 
shape of Quadrula tuberculata (Raf.) but the nacre of cooperiana 
(Lea) and I should call it that, although out of range. I never 
heard of tuberculata except with purple nacre.’’ A white nacred shell 
of the same form is considered by Prof. Clark as ‘‘rather plump, 
approaching granifera’’ but that the nacre “‘suggests cooperiana.”’ 
Other Missouri collectors have commented upon this strange 
departure of R. tuberculata and granifera from type. However, 
if it may be proved that this difference of nacre-color is merely 
a ‘fading out’’ due to chemical reaction of mineral water there 
would be instead of a true cooperianus in this state a mere local 
form of a Rotundaria. ‘The real home of this species is in the 
Tennessee—Cumberland system where Wilson and Clark (1914, 
pp. 44 and 60) have found it as a summer breeder (a tachytictic 
species). 
