THE NAIADES OF MISSOURI AAI 
subrostrata; epidermis black, glossy, rayed with broad reddish 
stripes. 
INTERNAL STRUCTURES:—Cardinals very long and _ stout, 
double in both valves; laterals long, somewhat pointed in male, 
more or less horizontal in female; nacre usually rich purple but is 
variable to white, or the two colors may be present for the same 
individual. 
Sex Length Height Diameter Locality 
o 125 xX 53 X 31mm—(Black R., Williamsville) 
9 109 x 48 x 3o0mm—(Osage R., Osceola) 
& 96 x 40 x 25mm—(Gasconade, Gascondy) 
9 78 x 30 x 18mm—(White R., Hollister) 
MISCELLANEOUS REMARKS:—No juvenile shells are at hand. 
Adolescent shells of recta are even difficult to obtain. Kecta is not 
a variable shell for this state; even in nacre-color it is rather 
constant—being more purple in Central Missouri and white in 
South and Southwest Missouri streams. This species has one of 
the widest distributions in the state; however, it is seldom found in 
the North Missouri streams. It is strictly fluviatile. According 
to Simpson it has a very general distribution over the United 
States, although it is not very common in its individual occurrence 
anywhere. The predominance of one sex over another in this: 
species for the same stream is more noticed than in any other. 
Probably this occurrence is due more to breeding season than to 
any other cause. The writer notes from his own record, and that 
of others, that this species is bradytictic. 
Surber (1913, p. 109) finds that the occasional host for recta 
to be the sunfish (L. pallidus). 
Genus Lampsilis Rafinesque. 
1820—Lampsilis Rafinesque, Monog., Ann. Gen. Sci. Phys. 
Brux. p. 298; 1900b, Simpson, Pr. U. S. Nat. Mus., XXII, p. 526. 
(Type, Unio ovatus Say.) 
ANIMAL CHARACTERS :—Branchial and anal opening papillose; 
supra-anal not very large, separated from the anal by a moderate 
connection; inner laminae of inner gills connected to the visceral 
mass, sometimes a small hole is left post-dorsad of foot; marsupium 
usually kidney-shaped, distended, consisting of many ovisacs 
which are distinct, extended below original edge of sterile marsu- 
