322 KANSAS UNIVERSITY SCIENCE BULLETIN. 



tooth in each valve, and sometimes a secondary tooth ; laterals 

 rarely present; muscle scars shallow. 



"Animal with the marsupium occupying the whole of the 

 outer gills, consisting of short, horizontal ovisacs, which run 

 directly across the gills, and are discharged through the 

 outer wall with the ovules in them ; ovules ten to twenty-five 

 in each ovisac and arranged in one or two rows, inner gills 

 the larger, free in part from the abdominal sac, or wholly 

 united ; mantle generally bordered behind with square black 

 spots ; branchial opening with numerous papilhe ; opening 

 papillose or crenulate." (Simpson.) 



Strophitus edentulus Say. Plate LXXII, fig. 1. 



Alasmodonta edentula Say, New Harm. Diss., il, No. 22, 1829, p. 340. 

 Anodonta wardiana Lea, Trans. Amer. Phil. Soc, iv, 1836, p. 46, pi. 



XIV, fig. 42. 

 Anodonta arkansasensis Lea, Trans. Amer. Phil. Soc, xi, 1852, p. 



293, pi. XXIX, fig. 56. 



Shell moderate to large, rather thin, but variable in this 

 respect, slightly thickened anteriorly, long elliptical, not 

 much inflated. Anterior margin rounded ; ventral margin 

 somewhat bowed ; posterior margin roundly triangulate, the 

 point of juncture of the two posterior margins being exceed- 

 ingly variable in its position ; dorsal margin straight, and 

 joined with the posterior at a very greatly varying angle. 

 Umboidal ratio approximately one-third of the entire length, 

 and quite constant. Umbones fairly prominent, but not 

 much raised, and ornamented with three or four coarse 

 ridges. Lines of growth quite continuous and very variable 

 in their prominence. Color of epidermis varies from light 

 horn to almost black ; young specimens marked with dark 

 green rays, old shells eradiate. Ligament stout, almost 

 black. 



Interior : Pseudocardinals represented by one or two 

 pearly nodules below or anterior to the umbones, hinge ridge 

 rather heavy. Anterior musclescars well marked ; anterior 

 adductor cicatrix sometimes slightly impressed; posterior 

 scars small but well marked, often fused. Pallial line hardly 

 apparent ; prominent lines of growth show on interior surface 

 as slight rounded ridges. Cavity of shell moderately deep, 



