352 THE AMERICAN MIDLAND NATURALIST 
very solid; glochidia very small, sub-ovate; spineless, hinge 
line short, slightly curved. 
SHELL CHARACTERS:—Shell thin, sub-elliptical, alated, com- 
pressed; post-umbonal ridge lacking; disk smooth; unbones 
low marked with fine concentric lines followed by later double- 
looped bars; epidermis glistening tawny, rayed; sex-dimorphism 
shown in wider more blunt vertically at posterior end of female 
shell; hinge teeth reduced to rudiments. 
MISCELLANEOUS REMARKS:—This genus is also constructed 
on the basis of characters relating to shell and glochidia rather 
than to anatomical structures. On basis of glochidial characters 
alone it classes with Amygdalonaias; however its shell characters 
throw it near to the genus Proptera. Lasmonos is represented 
in this State by its type (which is the commonest shell in North 
Missouri) and by simpsoni Feriss. The latter is grouped here 
tentatively until its soft parts are studied as its shell characters 
more closely relate it to the type of this genus than to any other. 
The species, Leptodea leptodon Rafinesque, is perhaps congeneric 
here and much depends upon its marsupial and glochidial characters, 
which are as yet unknown; however, the writer has not been 
fortunate enough to secure live specimens of this species (not 
even dead shells) in this State, but, because of the use Rafinesque 
made of it, we are concerned here for nomenclatural reasons, 
for should it be found to be really congeneric with fragilis, aside from 
ats several shell characters, the generic name, Leptodea, would take 
preference to the one herein used. 
Lasmonos fragilis Rafinesque. 
(Paper Shell,” “{Razor“Back.’?) 
Pl. IX, Fig. 19; Pl. XXVI, Figs. 90 A—D. 
1820—Lasmonos fragilis Rafinesque, Mono. Biv. of Ohio. 
1823— Unio gracilis Barnes, Am. Jl. Sci., VI, p. 274. 
1861— Unio dolosus Lea, Jl. Phil. Ac., V, p. 75. 
1900b—Lampsilis gracilis Simpson, Pr. U. S. Nat. Mus., XXII, p. 573. 
1912b—FParaptera gracilis Ortmann, An. Car. Mus., VIII, p. 331. 
ANIMAL CHARACTERS. 
‘NUTRITIVE STRUCTURES:—Branchial opening round, with 
spreading, yellowish tentacles; anal slightly crenulated, with thick- 
ened edges and normal diaphragm; supra-anal long, extending to 
dorsal ala, usually closed; mantles paralle] at edges, dark colored 
