H' 



178 THE NAIADES OF MISSOURI 



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 



<f 125 X 53 X 31mm — (Black R., Williamsville) 



9 109 X 48 X 30mm — (Osage R., Osceola) 

 cf 96 X 40 X 25mm — (Gasconade, Gascondy) 

 9 78 X 30 X 1 8mm — (White R., Hollister) 



Miscellaneous Remarks: — No juvenile shells are at hand. 

 Adolescent shells of recta are even difficult to obtain. Recta 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 fiuviatile. 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 brad3rtictic. 



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- 



