THE NAIADES OF MISSOURI 135 



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. Aherti is a rather common 

 little shell in the White, Black and Neosho basins of this State. 

 It is distinguished from C. irrorata 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 irrorata, 

 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 — Unio 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. 



