3, THE CHICAGO ACADEMY OF SCIENCES. 
Animal: Anal opening small, black, without papille; 
branchial opening rather large with crowded papillze; mantle 
border decidedly thickened; inner gill larger in front, free 
from the abdominal sac a short distance posteriorly; gills not 
united to each other to the posterior extremity, but joined to the 
mantle to their posterior end. Outer gill contained a few ova 
in the specimens examined. (Simpson. ) 
Distribution: Great Lakes and Mississippi Valley. 
Geological distribution: Pleistocene. 
Habitat: In rivers and creeks, under stones and other 
objects. It is also found in mud which is free from débris. 
Remarks: A small and characteristic species which is at 
once distinguished from all other species found in this region 
by its fragile shell, delicate hinge armature and minute beak 
sculpture. Next to Lampsilis parvus, it is the smallest species 
found in the region. The individuals from Hickory Creek are 
wonderfully uniform in shape and are readily identified by the 
peculiar swelling of the postérior part of the shell. This species 
also seems to be restricted to the Desplaines River and its trib- 
utaries, and is very abundant; when one is found, dozens or 
even hundreds of individuals may be found near by. 
* *K *K 
Ovules filling the entire outer gill Of the female, ovisacs 
short, running crosswise of the gill. (Simpson. ) 
Genus ANODONTOIDES* Simpson, 1898. New genus. 
Shell: Elongate oval, inflated, thin, with a smooth, bright 
epidermis, which is often faintly rayed; beaks full, beak 
sculpture much as in Strophitus, but less developed and more 
delicate, consisting of a few concentric ridges with slight radi- 
ating ridges behind but not in front; hinge line slightly 
incurved in front of the beaks; teeth wanting or reduced to mere 
vestiges; nacre not brilliant. 
Animal: Anal opening furnished with distinct papille; all 
four gills filled with embryos; inner branchiz united, wholly or 
in part, with the abdominal sac. (Simpson.) 
13. Anodontoides ferussacianus Lea, pl. iii., fig. 6; pl. v., fig. 2. 
Anodonta ferussaciana Lea, Trans. Amer. Phil. Soc., 2d series, Vol. V., 
p. 45, pl. vi., fig. 15, 1887. 
Shell; Rather thin, moderately inflated (much inflated pos- 
*The writer used the name Anodontopsis for this genus in his mollusks of Western 
New York (Trans. Acad. Sci. St. Louis, Vol. VIII., p. 76); Mr. Simpson has since stated 
that the name was preoccupied by McCoy for a genus of fossil Pelecypoda, hence the change 
of the name as above, 
