ORTMANN: FAMILIES AND GENERA OF NAJADES. 291 
latter. Besides there is no difference whatever in the gills. The 
slight differences mentioned cannot be regarded, under any conditions, 
as of generic value, in face of the great similarity of structure. The 
presence of papillae on the anal opening (Haas, 1910a, p. 110) in 
Pseudanodonta is a character, which at most has merely specific 
value. There remains only the glochidium (see Plate XIX, fig. 3) 
to be considered. There are, indeed, certain differences between the 
glochidia of A. complanata and cygnea, but as far as they are known 
in other members of the genus and subfamily, such differences are 
encountered elsewhere, without being considered as of generic value. 
The glochidia are undoubtedly built upon the same plan in both species. 
A. complanata not only is a true Anodonta, but judging by the shape 
of the beak and beak-sculpture belongs to that group in the genus, of 
which A. cygnea is the type. We cannot separate it generically from 
the latter, without disregarding natural affinities. 
Anodonta imbecillis Say. 
I have investigated twenty-three specimens from northwestern 
Pennsylvania (Allegheny and Lake Erie drainages), and two from 
Lawrence, Douglas Co., Kansas (R. L. Moodie). All were females in 
structure, and many were gravid. This species is hermaphroditic. 
Typically bradytictic, and gravid from September to May. In 
Lake Erie the time of discharging the glochidia is postponed even 
further, this act having been observed as late as July 12. 
The anatomy has been described by Lea (Obs., X, 1863, p. 449). 
Of all American forms this species resembles most closely the 
European Anodontas in the shape of the shell. It differs, however, 
in being hermaphroditic. The soft parts present no special features, 
and they agree both with the European A. cygnea and the: North 
American A. grandis. The anal opening is almost smooth. 
Glochidia smaller than those of cygnea, slightly higher than long 
(length 0.30; height 0.31 mm.), of the usual shape, with hooks (see 
ea Obs, Viv 1858; pl. 5, fig. 360; Ortmann, 1O11d, pl: 890,. fig. 13). 
Color of soft parts whitish, foot yellowish brown; gills pale brown; 
edge of mantle blackish. Charged marsupium brown. 
Anodonta henryana Lea. 
Seven specimens from a branch of the Rio Grande, Mercedes, 
Hidalgo Co., Texas, collected May 15, 1907, by Dr. D. A. Atkinson. 
