THE NAIADES OF MISSOURI IIS 



flat on the center of the disc, it may not be the typical dakota of 

 Frierson. In other respects the shell structures are identical 

 with those of A. grandis. 



Sex Length Width Diameter Locality 



9 114 X 78 X 48 (L- Contrary, St. Joseph, Mo.) 



cf 108 X 73 X 49 " (L. " " " " ) 



Miscellaneous Remarks: — This truncated form may only 

 be the result of a local reaction on grandis as it is not often found 

 in very quiet water but in the more disturbed water near the 

 shore, yet its occurrence in such a constant shell-form is so common 

 in our Missouri lakes that it would be safe to assign it to the defi- 

 nite species herein referred, or at least its subspecies. Dr. Ortmann 

 thinks this form may bear the same relation to our western lakes 

 as A. henediciis (a form of grandis-Jootiana) does to Lake Erie 

 where it is grown close to the shore in the surf. 



Anodonta corpulenta Cooper. 

 ("Big Floater," "Slop Bucket.") 



Not figured. 



1834 — Anodonta corpulenta Cooper, App. to Narrative, Exp. Miss. R. 

 to St. L., p. 154.— B. W. Wright Check List, 1888. 



Animal Characters: — The nutritive and reproductive struct- 

 ures are identical with those of A. grandis; however, its glochi- 

 dium is different in shape and size, having an irregular, undulate, 

 hinge line with length and depth equal (0.350 x 0.350mm.). 



Shell Characters: — With the exception of a shorter, 

 wider, more inflated shell and also of more recurved beaks the 

 shell is the same as that of A. grandis. 



Miscellaneous Remarks: — Some students of Naiades are 

 inclined to call corpulenta an "overgrown grandis." However, its 

 smaller, but most of all, its differently formed glochidium would 

 separate it from grandis since nothing is so constant as glochidial 

 characters. This form is reported as rather common in the sloughs 

 and lakes along the Mississippi in this state; yet it is not found 

 in the lakes of North-west Missouri. vSimpson reports it for the 

 Missouri river (1900b, p. 646) but is not specific about the locality 

 and states that it has a general distribution for the upper Mississ- 

 ippi River east to Indiana and south to Texas where it may be 

 replaced by A. stewartiana. Dr. Surber (1913, p. 106, PI. XXIX, 

 fig. i) has found this species to be an occasional fin-parasite upon 



