52 NAIADES OF MISSOURI 



where it has developed a heavier, less pustulous shell as we 

 note in the ecologic results for some shells of Amhlemae. This 

 form is reported also for the St. Lawrence basin as well as through 

 all the northern part of the Mississippi Valley, even down into the 

 South-west as far as Kansas and Oklahoma. The writer has been 

 able to keep a good breeding record for this very acessible form 

 for Missouri to find it only gravid through June and July. 



Quadrula pustulosa asperata (Lea). 



PI. XVII. Fig. 42 A and B. 



1861 — Unio asperatus Lea, Pr. ac. Nat. Sci. Phila. V, p. 41; Jl. Ac. 

 N. Sci. Phila., v., p. 68. PI. VII. Fig. 218. 



Animal Characters: — Soft parts have been examined 

 afield and found to be identical with those of the parent species. 

 None were found gravid. All four gills of sterile females were 

 marsupial in character through the test of finding more crowded 

 septa. 



SHELL CHARACTERS. 



External Structures: — Subtrigonal, very upright, higher 

 than long, post-umbonal ridge moderately inflated, dorsal line 

 rather straight, ventral margin abruptly curved, rounded pos- 

 teriorly, subtruncated anteriorly; beaks well forward and eroded; 

 tubercles few, disposed on upper part of disk; epidermis reddish 

 brown to black. 



Internal Structures: — Identical with those of type, pus- 

 tulosa except perhaps a broader, thinner and more upright 

 interdentum. 



Sex Length Height Diameter Locality 



<f 44 X 46 X 28mm (Osage R., Warsaw, Mo.) 



9 50 X 48 X 32 " ( " " Osceola, Mo.) 



d' 46 X 46 X 31 " ( " " Bagnell, Mo.) 



Miscellaneous Remarks: — The form of the above des- 

 cription is of rare occurrence in the Osage River, but still the 

 other form for this state, schooler ajtensis, does not occur much 

 oftener in this river. According to Mr. Bryant Walker this is 

 "a western form of Q. pustulosa and if it came from the Coosa 

 River, Alabama, it would surely be referred to Q. asperata (Lea)." 

 Comparisons to the actual shell from Alabama (Coosa R., Cedar 

 Lluff) shows it to be almost identical both as to external and 

 internal features. 



