Ortmann: Families and Genera of Najades. 343 



Eurynia (Eurynia) nasuta (Say). 



Numerous specimens have been investigated, partly from Lake 

 Erie, partly from the Delaware drainage in eastern Pennsylvania and 

 New Jersey. 



According to Conner (1907, p. 88) this species breeds all the year 

 round, that is to say, the end of one breeding season overlaps the 

 beginning of the next in midsummer. This refers to the Delaware 

 drainage in eastern Pennsylvania. For this region I have only a few 

 observations (in the months of September and May). From Lake 

 Erie I have specimens with eggs collected at the end of August (be- 

 ginning the breeding season), and others with glochidia collected in 

 May, June, and as late as July 7. On the latter date specimens in 

 the act of discharging were observed. But there is surely an "in- 

 terim" in Lake Erie, at least in July, for of all the specimens collected 

 on July 8, 12, 22, and 23, not a single one was gravid, although numer- 

 ous sterile females were among them. 



The soft parts have been described by Lea (Obs., X, 1863, p. 403), 

 but in error the marsupium is said to occupy the whole length of the 

 gill. The papillae of the edge of the mantle have been described by 

 Ortmann (1911b, p. 317). 



The inner edge of the mantle of the female has in front of the 

 branchial a rather regular row of numerous (as many as thirty and 

 more) rather closely set, subequal papilla?, which are rather small, 

 subconical, and run forward to almost the middle of the ventral margin, 

 where they disappear gradually and pass into the smooth anterior 

 part of the edge. This row is not accompanied by a distinct black 

 band, but there is brownish pigment in this region. Marsupium 

 formed by over half (up to three-fourths) of the outer gills, with a very 

 small non-marsupial section behind. Ovisacs fifteen to forty, their 

 ends having no black pigment. Glochidia (Lea, Obs., XIII, 1874, 

 pi. 21, fig. 2), similar in shape to those of the preceding species, rather 

 large. Length 0.25; height 0.29 mm. (see Plate XX, fig. 8). 



Mantle-connection between anal and supra-anal rather long, 

 longer than the anal. Inner lamina of the inner gills connected with 

 the abdominal sac, often with a small hole at the posterior end of the 

 foot. Posterior margins of palpi connected only at base. 



