NAIADES OF MISSOURI 143 
dorsad, color of soft parts tan, for most part, mantle edges at 
siphonal openings black, gills and parts above darker tan tha 
parts below. 
REPRODUCTIVE STRUCTURES :—Only sterile marsupia observed; 
all four gills, however, marsupial and same in structure as that 
of Q. verrucosa; glochidium not found. 
SHELL CHARACTERS. 
EXTERNAL STRUCTURES :—Shell roughly pentagonal in gen- 
eral outline, heavy, thick, solid, compressed posteriorly, inflated 
for one-half of the shell anteriorly, obtusely biangulated behind 
with truncation obliquely antero-ventrad, broad, shallow, radial 
furrow, post-umbonal ridge flattened and sculptured with few 
tubercles, area in front of radial furrow irregularly and coarsely 
tuberculated, slopes of post-dorsal ridge with low upcurved 
costae, epidermis dark brown, growth lines coarse. 
INTERNAL STRUCTURES:—Cardinals and laterals both dis- 
tinctly doubled in the two valves, interdentum short, wide, 
cut away in right valve for the post-left cardinal, anterior adductor 
muscle scars usually drawn to the front, nacre milky white. 
Sex Length Height Diameter Locality 
OM T20eX Son kn) 5), 11m (Marais des Cygnes R., Rich Hill,) 
ee SOn, Suey ONeXe 1 SO am (Osage R., Greenwell Ford) 
Se EMSS ear Gu ech ool, She t se ye ae ae) 
No juveniles were obtained. The last measurement, is that 
of the smallest in the writer’s collection, but shows no real juvenile 
characrters, and is more like Q. aspera except for its difference 
in posterior biangulation and also in its tuberculation. 
MISCELLANEOUS REMARKS:—Simpson (1900b, p. 776) puts 
Q. nobilis down in the synonomy of aspera, but later refers it to 
Q. verrucosa. However, from studies of its peculiar anatomy and 
internal shell structures it may come very near to verrucosa. ‘This 
is a rather common species for the Osage where it reaches a larger, 
heavier growth of shell than is ever attained by verrucosa. It is 
also a broader, shorter shell with great solidity and inflation 
anteriorly and also greater compression posteriorly. Noodilis is 
reported by Isely (1914, p. 4) for the lower Neosho basin. It 
likewise appears occasionally in this same drainiage for Missouri 
and is also found in the Grand River of North Missouri. Like R. 
tuberculata (Raf.), nobilis may be said to have no true supra-anal . 
opening due to its lack of mantle connection between the anal and 
