NAIADES OF MISSOURI 139 
heavy shell, that occurs in the Mississippi Valley, North of the 
Ohio and also of the Missouri Rivers. The differences in this 
upright, rounded shell from its parent are stated in the compara- 
tive description. Since students of Naiades have pronounced it 
a variety, if found in sufficient numbers, the author concurs by 
naming it for its type locality, Lake Contrary, St. Joseph, Mo. 
Wherever found in this lake, the bottom is a soft, marly mud, 
and the situations are in rather deep water sheltered from wave 
action. The author has discovered a short period breeding season 
for contraryensts. 
Quadrula nodulata Rafinesque. 
(“Pimple+Back,”’ ““Warty Back.’’) 
Plo XV LES igs) 44° 2) and. B: 
1820—Obliquaria nodulata Rafinesque, Bivalves of River Ohio, Ann. 
Gen. Sci. Phys. Brux. 
1834— Unto pustulatus Lea, Tr. Am. Phil. Soc., p. 79, Pl. VII, fig. 9. 
1834— Unio nodulatus Say, Am. Conch., VI. 
ANIMAL CHARACTERS:—Nutritive structures absolutely iden- 
tical with those of Quad. pustulosa (Lea). The glochidial characters 
are the same, except a difference in size, the glochidium of nodulata 
being the larger 0.230 x 0.290 mm. However, small differences 
in size may not be considered good distinctions as it is the glochi- 
dial jorm that is to be taken into greater account. 
SHELL CHARACTERS. 
EXTERNAL STRUCTURES:—Shell medium in size, solid, sub- 
orbicular, inflated, post-dorsal ridge projected; umbones very 
full, ‘high, incurved bearing three or four small corrugated, con- 
centric ridges; post-umbonal ridge and central part of disk orna- 
mented with two radial rows of small, erect pustules sometimes 
terminating with half-tubercles at ventral margins; epidermis 
light tan to dark horn. 
INTERNAL STRUCTURES:—Identical with pustulosa. 
Cease keetA Ole oxi 30 mm 0.200 (Miss. R., Hannibal, Mo.) 
Od Sex SS URN SSCS GOVZIS OMAN MERI a az) 
CHa eX ZO EX bi 7% Or2zTOw = ( 
Shell of juvenile subglobose, post-umbonal ridge prominent, 
post-dorsal ridge short, high; tubercles few in two rows—one on 
post-ridge—no radial furrow between; beaks very full, sculptured 
” 
” ”” 3 ”” ) 
