456 THE AMERICAN MIDLAND NATURALIST 
out sculpture. Female shell broader posteriorly, marsupial expan- 
ston formed post-ventrad, above basal line just anterior to post- 
umbonal ridge and bounded ventrad by a furrowed rest line. Male 
shell more trigonal in shape with post-umbonal ridge rather 
biangulated and with a very slight radial furrow in front; dorsal 
ridge rather prominent. 
Internal structure of both sexes about the same except a 
higher mantle line in the female shell; cardinals double in both 
valves; laterals single in right, double in left; branchial cavities 
deeply basin-like; nacre blue with a tinge of yellow in the bran- 
chial cavity, irridescent posteriorly. 
Sex Length Height Diameter Locality 
9 32 x 21 x 15mm—(Black River, Williamsville) 
o& 26.5 x 18 x 14mm—(Black River, Williamsville) 
MISCELLANEOUS REMARKS:—Although this rare Species has 
been found only in one locality yet a sufficient suite of shells was 
secured to establish its novelty. One specimen was obtained 
gravid with ova, yet it was sufficiently, although briefly, described 
afield before it was lost as often results in a rush of field work. 
At first the author was inclined to call this Species 7. triquetra, 
but comparisons to actual shells of typical triquetra show that it 
is placed in the third group of Truncilla which is characterized by 
the marsupial expansion formed by the inflation just anterior 
to the post-umbonal ridge not extending below the basal line 
and in which group triquetra is not classed. Lefevre differs from the 
arcaeformis of Lea in not possessing a radial depression in front 
of the post-dorsal ridge and in not having such a prominently 
curved post-umbonal ridge and also in not possessing such coarse 
hinge teeth. This new and most modern Species is dedicated to Dr. 
‘George Lefevre of the Department of Zoology in the University of 
Missouri. The discovery of this new Species from the Black River, 
Williamsville, Missouri, and also of the new Truncilla, Curtisw Frier- 
onand Utterback, from the White River, Hollister, this State, and, 
being the only completely described 7runcillae west of the Mississ- 
ippi, it seems fitting that these should bear the names of the two 
associate authors and instructors who have contributed so much to 
the science of the Nazades in their monumental work, ‘‘ Studies on 
ihe Reproduction and Artificial Propagation of Fresh-Water Mussels.”’ 
(THE END) 
