282 Annals of the Carnegie Museum. 



lateral, or secondary, water-tubes, while the middle portion forms the 

 ovisac, which is also closed at the base of the gill. The eggs fill the 

 ovisacs in densely crowded masses, and in certain places a placenta- 

 like cohesion may be observed. But when the glochidia are mature, 

 they are perfectly free, and no indications of placenta? are seen. 

 Glochidia subtriangular, almost semicircular, longer than high, with 

 hooks. Length 0.34; height 0.28 mm. (see: Lea, Obs., VI, 1858, 

 pi. 5, fig. 23; and Ortmann, 1911&, pi. 89, fig. 10). 



Color of soft parts whitish, edge of mantle black, chiefly so poste- 

 riorly. The foot is pale brownish yellow, the gills grayish. The ab- 

 dominal sac is often pinkish. The charged marsupium varies greatly 

 in color, this variation depending at least in part on the stage of de- 

 velopment of the embryos. It may be white, cream-color, pinkish, 

 pale orange, or various shades of brown. 



Symphynota viridis (Conrad). 



Numerous specimens have been investigated from the Potomac, 

 Susquehanna, and Delaware drainages of eastern Pennsylvania. 



Breeding season from August to May. 



Soft parts described by Lea (Obs., XIII, 1874, p. 71). They are in 

 every particular identical with those of S. compressa. This species also 

 is hermaphroditic (Ortmann, 191 lb, p. 310), and specimens with the 

 male structure of the gills have never been found. Glochidia (Lea, 

 ibid., pi. 21, fig. 4) are about of the same shape as those of the fore- 

 going species, but slightly larger. Length 0.36; height 0.30 mm. 

 Color of soft parts as in compressa; marsupium cream-color, pale orange, 

 or brown. 



Symphynota complanata (Barnes). 



Eight specimens from northwestern Pennsylvania, collected by my- 

 self, have been investigated; in addition, three from the Kansas 

 River, Lawrence, Douglas Co., Kansas (R. L. Moodie), and one from 

 the Ohio at Portland, Meigs Co., Ohio (collected by myself). Among 

 them were males, sterile and gravid females. 



Breeding season not completely known, but the dates at hand agree 

 with those of other species. Eggs were found in the marsupium in 

 September. 



Lea (Obs., X, 1863, p. 448) has described the soft parts; Simpson's 

 (in Baker, 1898, p. 61) description is partly incorrect (scalloped edge 



