450 THE AMERICAN MIDLAND NATURALIST 
sisting of thirty large ovisacs distended, when gravid, at their 
distal ends into bulging beads drawn down near to mantle flap 
which is a long, wide, ragged ribbon that bears eye spots and 
extends to bend of the post-ventral curve of the shell; congluti- 
nates white, discharged in unbroken masses; glochidia medium 
in size, semi-elliptic, with rather straight hinge line, measuring 
0.205 X 0.255mm. 
SHELL CHARACTERS. 
EXTERNAL STRUCTURES:—Shell of female sub-rhomboidal 
greatly inflated, swollen post-ventrad, male sub-elliptic not so 
- inflated; narrowly rounded before, disk smooth, without sculpture; 
beaks very full, very much inflated, sculptured by four coarse 
sub-parallel bars with rounded furrows between; epidermis thin, 
smooth, polished, yellowish, bluish olivaceous or even terra- 
cotta, with broad brilliant green, or blue-green rays all over shell; 
post-umbonal ridge prominent but not angled. 
INTERNAL STRUCTURES :—Cardinals prominent, serrate, rather 
curved; laterals erect blade-like; beak cavities very deep and 
basin-like; nacre pure marble white, sometimes inclined to pink. 
Sex Length Height Diameter Locality 
9 100 x 65 x 45mm—(Gasconade R., Gascondy) 
os 90 x 65 x 42mm—(Black R., Williamsville) 
co 110 x 39 x 26mm—(Osage R., Osceola) 
9 55 xX 39 x 26mm—(Miss., R., La Grange) 
The young shells are very bright colored. The specimen 
of the last measurement has a blue epidermis with bright blue- 
green stripes. Its beak sculpture is very plain and eroded in curved 
beaks showing as above described. No juveniles obtained. 
MISCELLANEOUS REMARKS:—Young shells look much like 
multiradiata but can be distinguished from the latter by the presence 
of post-umbonal ridge and by not possessing so many finer rays. 
The adult shell is told from that of ovata by not possessing the 
sharp cornered post-ridge, larger shell and more peculiar rays. 
Aside from these two related shells ventricosa is unique. Multira- 
diata and ovata are not found in Missouri. Ventricosa is also very 
peculiar in the structure of its soft parts—especially in the great 
development of the mantle flap that characterizes the genus 
Lampsilis. The writer has observed these flaps extended and in 
action both. in the aquarium and in nature. Three have been seen 
