ORTMANN: FAMILIES AND GENERA OF NAJADES. 341 
Hinkley, Nov. 5, 1910; and two males from the Ouachita River, Arka- 
delphia, Clark Co., Arkansas, collected by H. E. Wheeler, Feb. 6, 1911. 
In front of the branchial there are about ten to twelve cylindro- 
conical papillae of medium and unequal size, the smallest near the 
branchial, the largest forward. They are slightly distant from each 
other, and stop suddenly before reaching the middle of the lower 
margin. Marsupium formed by the posterior half (or more) of the 
outer gill. Ovisacs fifteen to twenty-two. No black pigment on 
margin of marsupium. Glochidia rather large, subovate. Length 
0.20; height 0.27 mm. (see Plate XX, fig. 5). 
In all other respects like EF. trabalis and E. vibex. 
Eurynia (Micromya) iris (Lea). 
Four males one sterile and six gravid females have been investi- 
gated, coming from the Ohio and Lake Erie drainages in western 
Pennsylvania. 
Gravid females have been found in the months of September and 
May; sterile females in May, June, and July. Thus the breeding 
season seems to be normal. 
The soft parts (of iris and novi-eboraci) have been described by Lea 
(Obs., X, 1863, p. 419) and Simpson (in Baker, 1898, p. 106). 
Fic. 23. Eurynia (Micromya) iris (Lea). Gravid female from Little Beaver 
Creek, Enon Valley, Lawrence Co., Pa. (Carn. Mus., No. 61, 2,159.) Coll. May 
II, 1907. 
In front of the branchial (see Ortmann, 19110, p. 317) there are four 
to ten large, conical papilla, which are quite distant from each other, 
with a few smaller ones between them. They do not reach to the 
middle of the lower margin. Marsupium formed by the posterior 
half (or less) of the outer gill, with a very small non-marsupial section 
at the posterior end. Ovisacs thirteen to twenty-two. Edge of 
