THE NAIADES OF MISSOURI 143 



daily throughout July and the first two weeks of August to find 

 them sterile in every case. Since Wilson and Clark (191 2, 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, pi. II, fig. 4. 

 1900b — Lampsilis venustus Simpson, Proc. U. S. Nat. Mus., XXII, 

 P- 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- 

 /orm w-shell except for a small 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 



cf 60 X 37 X 22mm (Niangua R., Hahatonka) 



9 55 X 31 X 22mm ( " " " ) 



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 

 ellipsiformis. 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 A", ellipsiformis there should 

 be no hesitancy in naming venusta as a variety. From N. pleas ii 

 this subspecies differs by a ticker, heavier, more coarsely rayed 

 and more of a tawny clolored shell. 



Nephronaias Pleasii (Marsh). 

 ("Bleeding Tooth," "Pleas' Shell.") 

 PL XXV, Figs. A—D. 



1891 — Unto pleasii Marsh, "The Observer" (a newspaper), II, May; 

 Nautilus, V. p. 2. 



iQOob — Lampsilis pleasii Simpson Pr. U. S. Nat. Mus., XXII, p. 557. 



Animal Characters: — No females have been secured bv the 



