Ortmann; Families and Genera 01 Najades. 293 



Color whitish. Foot orange-yellow, palpi and gills brown. Edge 

 of mantle brown, black behind. Charged marsupium yellowish white 

 (with eggs) to liver-brown (with glochidia). 29 The orange tint of 

 the foot is variable, lighter or darker. 



Anodonta cataracta Say. 

 About twenty-five specimens from various places in the Atlantic 

 drainage of eastern Pennsylvania have been investigated. 



The breeding season begins in August, in which month 1 repeatedly 

 found gravid females with eggs. 1 have no other observations of 

 my own, but Conner (1907, p. 88) gives October to May as the breeding 

 season. 



Lea (Obs., II, 1838, pi. 15, fig. 46) has figured the animal, but his 

 figure is practically useless. 



The soft parts resemble in every respect those of A. grandis. I have 

 seen the glochidia of specimens from the Delaware River, collected 

 by C. H. Conner on March 19, 191 1, and they agree with the figure 

 published by Lefevre and Curtis (1910, p. 97, fig. C); the dimensions 

 are: length 0.36; height 0.37 (identical with those of the glochidia of 

 A. grandis). The colors of the soft parts are also the same. 



I have my doubts as to the specific distinctness of this form from 

 A. grandis. At any rate, it is merely the eastern representative of the 

 western grandis, and does not have any close affinity to the European 

 species and the Anodontas of the Pacific slope of America, as Walker 

 (1910a, p. 135) believes, and there is no reason to think that "it was 

 a co-immigrant with Margaritana margaritifera to the east coast of 

 North America" (from Europe). A. cataracta is, if anything, an east- 

 ern offshoot of the A. grandis-stock. of the central basin. 



Genus Anodontoides Simpson. (1898.) 

 (Simpson, 1900b, p. 658.) 



Shell subelliptical, thin, inflated, with smooth disk. Beak-sculpture 

 distinct, but not very heavy, consisting of concentric ridges curved 

 up behind, not double-looped. Hinge-teeth absent, or represented 

 by the merest rudiments. 



Soft parts much like those of Anodonta. Outer gills alone marsupial, 

 when charged distending at the edges, and secondary water-tubes 

 present, ovisacs not subdivided. Xo placentae developed. Inner 



29 Sometimes the light color is preserved in the glochidial-stage. 



