182 THE NAIADES OF MISSOURI 



is a dweller along the edges of muddy streams or in ponded stretches 

 of the rivers and prefers lacustrine situations. For that reason it 

 is commonly known as "Slough Sand Shell," and "Creeper." 

 Mr. Walker makes the assertion that typically these two species 

 are very distinct, but that it is frequently difficult to name indi- 

 vidual specimens so given are they to intergrading. The fact, too, 

 that both forms are found in the same stream (as in the Chariton 

 R., for instance) and apparently entirely distinct would go to show 

 that they are specifically distinct. Besides Surber (1912, p. 5) 

 states a difTerence in size of glochidia, those of Jallaciosa being 

 larger (0.200 x 0.240 mm.) than those of anodontoides (0.185 x 

 o.2iomm.). 



Surber (1913 p. 107) also reports that this species {jallaciosa) 

 has for its fish host the erappie (P. platorhynchus) its glochidium 

 being a gill parasite. 



Lampsilis Higginsii (Lea). 

 ("Higgin's Shell.") 

 PL XXVIII, Figs. 105 A and B. 



1857 — Unio higginsii Lea, Pr. Ac. N. Sci. Phila., IX, p. 84. 



1900b — Lampsilis higginsii Simpson, Pr. U. S. Nat. Mus., XXII, p. 540. 



Animal Characters : — As only dead shells of this species have 

 been secured by the writer no description of the soft parts can 

 appear here. Surber (19 12 p. 9) reports its glochidium as sub- 

 elliptic, spineless, with hinge line short and measures 0.210 x 

 0.260 mm. 



SHELL CHARACTERS. 



External Structures: — Shell very thick; male sub-elliptic; 

 female subrhomboid with posterior end vertically truncate; beaks 

 very large, rovmded, full, sculpture unknown; epidermis brownish- 

 red with rays. 



Internal Structures: — Cardinals large, erect; laterals 

 straight in female; slightly curved in male shell; interdentum wide, 

 thick; beak cavities deep; scars deep; nacre rosy pink to salmon. 



Sex Length Height Diameter Locality 



cf 86 X 63 X 45mm — (Mississippi R., Hannibal) 



9 68 X 50 X 38mm — ( " " " ) 



cf 85 X 48 X 48mra — { " " Louisiana) 



