Ortmann: Families and Genera of Najadi 341 



Hinkley, Nov. 5, 1910; and two males from the Ouachita River, Arka- 

 delphia, Clark ('«>., Arkansas, collected by 11. 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 E. 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). 



mp PP 



Fig. 23. Eurynia {Micromya) iris (Lea). Gravid female from Little Beaver 

 Creek, Enon Valley, Lawrence Co., Pa. (Cam. Mus., No. 61, 2,159.) Coll. May 

 11, 1907. 



In front of the branchial (see Ortmann, 191 lb, 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 



