THE NAIADES OF MISSOURI 343 
daily throughout July and the first two weeks of August to find 
them sterile in every case. Since Wilson and Clark (1912, p. 48) 
report it gravid for an earlier date this incomplete breeding would 
indicate that it is bradytictic. 
Nephronaias ellipsiformis venusta (Lea). 
Not figured. 
1838— Unio venustus Lea, Tr. Am. Phil. Soc., VI, pl. II, fig. 4. 
1900b—Lampsilis venustus Simpson, Proc. U. S. Nat. Mus., XXII, 
Pp. 543.- 
ANIMAL CHARACTERS:—Entirely identical with those of the 
species both as to nutritive and reproductive structures. No glo- 
chidia have been found. 
SHELL CHARACTERS:—Also identical with the typical ellipsi- 
formis-shell except for a smal) guttered furrow just antero-parallel 
to post umbonal-ridge of shell. The male shell of this sub-species 
is also more pointed posteriorly than the male type species. 
Sex Length Height Diameter Locality 
Om OO) ky 37 Sk 22TH (Niangua R., Hahatonka) 
OES ts ai ke 22 TI ( x ¥ 4 ) 
MISCELLANEOUS REMARKS:—The writer heartily agrees with 
Mr. Walker that venusta is very closely related to ellipsiformis 
and also with Mr. Frierson’s opinion, that it is only a form of 
ellapstiformis. The type locality for U. venustus of Lea is Potosi, 
Washington County, Missouri, and belongs to the Meramec River 
basin. Simpson (1900b, p. 543) only reports it for that locality. 
Since then Rev. Wheeler has reported it for Arkansas; so has 
Wilson and Meek (1912. p. 19.). The writer has only found it 
in the Niangua River. Having such limited distribution and such 
lack of discriminating features from JN. ellipsiformis there should 
be no hesitancy in naming venusta as a variety. From N. pleas 
this subspecies differs by a ticker, heavier, more coarsely rayed 
and more of a tawny clolored shell. 
Nephronaias Pleasii (Marsh). 
(““ Bleeding Tooth,” !/ Pleas’ Shell.’’) 
PGA Vie apse A) 
1891— Unio pleasit Marsh, ‘‘ The Observer’’ (a newspaper), II, May; 
Nantilias, Vi. wp. 2: 
1900b—Lampsilis pleasit Simpson Pr. U.S. Nat. Mus., XXII, p. 557. 
ANIMAL CHARACTERS:—No females have been secured by the 
