326 THE AMERICAN MIDLAND NATURALIST 
Sex Length Height Diameter Locaiity 
OU BOLA Xu) WOM akan AG (Grand River, Sumner) 
Si FOL x) N55. eke sO (Mississippi River, Hannibal) 
Oe FOR Within Seti ae Aer (Osage River, Warsaw) 
Gs Soy ex haar ox Tens (Mississippi River, Hannibal) 
Ue 2S Xe ee Oe ko ele ( ee us ng ) 
Beaks of these specimens of the last two measurements very 
full, rounded, poorly sculptured although not eroded; more 
inflated (comparatively) than adult shell; epidermis olive with 
profuse paintings of green rays so as to give the appearance of 
olive. green; post-ventral edge of shell more obliquely rounded 
than in adult; nacre pearl blue. 
MISCELLANEOUS REMARKS:—From shell characters there is 
no real sex dimorphism except a little greater inflation in the 
female, but not only a less crowded arrangement of septa is seen 
in gills of the male but there is a more intense black pigmentation 
in the region of the branchial opening. The crenulated supra-anal 
opening 1s surely a unique character and may indicate a conversion 
of this opening into the anal. The bare connection between the two 
openings would also indicate this merging. Although of rare 
occurrence ellipsis reaches its greatest perfection for the interior 
in the Grand River of North Missouri. It is found occasionally 
in the Osage Basin, but never develops a shell as large, heavy 
or bright as found in the Grand or in the Mississippi. This fact 
of difference in size, color and solidity for the shells of these different 
mussel faunae applies to most other species as well. Scammon 
(1906, p. 306) reports this species as very active with strong 
musculature and that he has traced this species for fifty yards 
by its furrow in the Kansas River. This species is bradytictic. 
Genus Nephronaias Crosse and Fischer. 
1893— Nephronaias Crosse and Fischer, Miss. Sci., Pt. 7, II, p. 556; 
1900b, Simpson, Proc. U. S. Nat. Mus., XXII, p. 591. 
(Type, Unio plicatulus Charpentier.) 
ANIMAL CHARACTERS:—Identical with those of Obovaria— 
even in glochidial characters. 
SHELL CHARACTERS:—Shell rounded to sub-elliptic and 
elongate, usually compressed; posterior ridge rather indistinct, 
beaks not near the anterior end, sculpture poorly developed,— 
consists of a few faint double-looped bars; epidermis greenish 
