THE NAIADES OF MISSOURI 445 
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 difference in size of glochidia, those of fallactosa being 
larger (0.200 x 0.240 mm.) than those of anodontotdes (0.185 x 
o.210mm.). 
Surber (1913 p. 107) also reports that this species (fallaciosa) 
has for its fish host the crappie (P. platorhynchus) its glochidium 
being a gill parasite. 
Lampsilis Higginsii (Lea). 
. (“ Higgin’s Shell.’’) 
Pl. XXVIII, Figs. 105 A and B. 
1857— Unto higginsit Lea, Pr. Ac. N. Sci. Phila., IX, p. 84. 
1g00b—Lampsilts higgtnsit 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 (1912 p. 9g) 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, rounded, 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 
So 86 x 63 x 45mm—(Mississippi R., Hannibal) 
9 68 x 50 x 38mm—( ab - a ) 
‘| 85 x 48 x 48mm—( 3 ” Louisiana) 
