344 THE AMERICAN MIDLAND NATURALIST 
writer; however, the nutritive structures of the males are identical 
with those of N. ligamentina and ellipsiformis. 
SHELL CHARACTERS. 
EXTERNAL STRUCTURES:—Shell sub-elliptical, rather thin, 
smooth, somewhat compressed, rounded before, obtusely angular 
behind; beaks rather low, scuJptured by three or four fine shaped 
undulations; epidermis brown polished horn, with numerous green 
capillary rays, disposed mostly posteriorly and showing through 
the thin shel]l on the inside. 
INTERNAL STRUCTURES:—Cardinals small, single in right, 
double in left valve, erect and parallel with laterals; left inter- 
dentum cut away for post-cardinal tooth; beak cavities rather 
shallow; nacre bluish, coppery or salmon in umbonal cavity. 
Sex Length Height Diameter Locality 
of IG! Sey oir IG, Tala (White R., Hollister) 
Sta SHAS ee Baca es ey Giaabin (hie? ae a ) 
Ce NONE Xe Oh Se Xa ene (James R., Galena) 
MISCELLANEOUS REMARKS:—According to Mr. Marsh this 
shel] bears some resemblance to Unio spatulatus Lea (i. e., U 
ellipsiformis Conrad), but differs chiefly in being thinner, smaller 
and more compressed. It is like venusta in that the female shell 
is deeply emarginate or constricted in front of post-umbonal ridge 
as the writer determines from the author’s description (1891, p. 2). 
This species was dedicated to Mr. Elwood Pleas of Indiana who 
collected this Species, together with many other rare Species, 
from South Missouri. It was also collected by Mr. S. M. Godbey 
at Morrisville, Polk Co., Missouri, who sent it to the National 
Museum where it is now recorded under the number, 132634. 
The writer found pleasii as a rather common shell in the White 
River, this State. 
Nephronaias ozarkensis (Call). 
(‘‘The Ozark Shell.’’) 
(Not figured.) 
1887— Unio ozarkensts Call, Pr. U.S. Nat. Mus., X, p. 498, pl. XXVII; 
1895, Tr. Ac. Sci. St. Louis, VII, pp. 33-34, Pl. XVIII. 
1900b—Lampsilis ozarkensis Simpson, Pr. U. S. Nat. Mus., XXII, 
Pp. 557- 
ANIMAL CHARACTERS:—Reference to rough field notes show 
