THE NAUTILUS. 43 



c 1 Shell large, ovate-rhomboid, high and short. Beak 

 sculpture sharply double-looped. Radial ridges 

 upon posterior slope present or obsolete. 



Subgenus : Pterosygna Rafinesque. 



c 2 Shell rather large, subrhomboidal or subtrapezoidal, 

 moderately long. Beak sculpture coarse, less dis- 

 tinctly double-looped (only sinuated). Radial 

 ridges upon posterior slope well developed. 



Subgenus : Lasmigona Rafinesque. 

 SYMPHYNOTA (ALASMINOTA) HOLSTONIA (Lea) (See: Ala^smi- 



donta h. Simpson, 1900, p. 670). 



On September 19, 1912, I collected two males in Clinch 

 River, Tazewell, Tazewell Co., Va., and on September 20, one 

 gravid female, with glochidia, in the same river at Richland, 

 same county. 



Anal separated from supraanal by a mantle-connection, 

 which is rather short, shorter than the anal, its inner edge dis- 

 tinctly crenulated. Branchial with papillae. Posterior mar- 

 gins of palpi united for about one-half of their length. 



Inner lamina of inner gills free from abdominal sac, except 

 at anterior end. Structure of gills Anodontine : in the gravid 

 female, only the outer gills are marsupial, they have lateral 

 water canals, and their edge is more or less distended. Glo- 

 chidia of typical shape, subtriangular, with hooks, large, 

 slightly higher than long. Length 0.32, height 0.38 mm. 



ANODONTA OREGONENSIS Lea (Simpson, 1900, p. 628). 



Twelve specimens, mostly females and gravid, in part with 

 glochidia, have been obtained from T. Kincaid. They were 

 collected in autumn 1911 in ponds near Seattle, King Co., 

 Washington. 



Soft parts of the type of the genus Anodonta: anal opening 

 small, its inner edge indistinctly crenulated or almost smooth. 

 Supraanal somewhat longer than the anal, widely remote, 

 about twice its own length, from the anal. 



Glochidia large, subtriangular, with hooks. Length 0.33- 

 0.34, height 0.32-0.33. The difference between height and 

 length is minimal. These Glochidia agree well with those of 



