THE NAIADES OF MISSOURI 323 
Although the shell of the last measurement is young and well 
preserved, yet the beak sculpture does not even present anything 
very distinct. The beaks are pointed, incurved and two-ridged,— 
one ridge radiating off to the posterior and the other to the anterior 
umbonal slope. The shell in this stage resembles that of young 
P. securis from a dorsal view. The soft parts of this specimen 
show that its marsupial characters consist of seven sterile ovisacs 
originating just in front of the middle part of outer gill curved 
backward toward the branchial opening. 
MISCELLANEOUS REMARKS:—C. Abertt is a rather common 
little shell in the White, Black and Neosho basins of this State. 
It is distinguished from C. zrrorata by not being so rounded, 
nor so solid, rugose and ridged parallel to growth lines. It is not 
to say a variable shell, yet the writer has noted some with such a 
truncated posterior end as to suggest an approach to zrrorata, 
or is probably the C. Aberti lamarckiana (Lea) reported for the 
Black River, Missouri. Specimens taken from Indian mounds 
in Southwest Missouri show great preservation although deposited 
some centuries ago. As they were placed in these graves for “‘food”’ 
to the departed spirit’’ (as was the burial custom of the aborigines) 
in greater quantities than other mussel shells it is evident that this 
species was prized above all others for its food qualities. It can 
be determined that the live mussels were deposited since dried 
muscular tissue is still adhering to the muscle scars. 
Cyprogenia Aberti lamarckiana (Lea). 
(Not figured, nor described.) 
1852— Unto lamarckianus Lea , Tr. Am. Phil. Soc., X, p. 266, pl. XVII, 
fig. 20. 
This sub-species is simply listed for this State through a report 
of it by Mr. Elwood Pleas to the U. S. National Museum, where 
it is now on exhibit under the number, 124,630—and also through 
a recent report of it for the Black River, Popular Bluff, Missouri, 
by Mr. Walker who has received it in this same collection of Mr. 
Pleas, a part of which lot was sent to the Washington Museum. 
No data is at hand for illustration or description. 
