Occasional Papers of the Museum of Zoology BG) 
- This species has become the type of Lasmigona by elimina- 
tion of the other species mentioned by Rafinesque (Alasmi- 
donta marginata Say), as first pointed out by Simpson. 
ANODONTA IMBECILLIS Say, 1829 
Type locality: Wabash River. 
Anodonta (Lastena) ohiensis Rafinesque, ’20, p. 50. 
Anodonta imbecilis Say, Walker, ’18¢, p. 176. 
U. levissimus (Lea) = An. ohiensis Raf., Conrad, ’34, p. 70; Ferus- 
SAG soap eee 
Anodonta imbecillis Say, Simpson, 714, p. 395. 
Lastena ohiensis (Raf.), Utterback, ’16, p. 109. 
Anodonta imbecillis Say, Walker, ’18¢, p. 176. 
Anodonta ohiensis Raf., Ortmann, ’19, p. 162. 
There is nothing in the original description of 4. ohiensis 
Raf. that supports the assumption that it is the well-known A. 
imbecillis Say. In fact, the most striking character of tnbe- 
cillis distinguishing the shell from other Anodontas, the 
depressed beaks, is not mentioned. Rafinesque gives for the 
subgenus Lastena, in which he places ohiensis, differential 
characters of the hinge: “two obtuse, transversal ridges, nearly 
lamelliform, divergent from each side of the beak.” Nothing 
corresponding to this is seen in imbecillis. In addition he says, 
“Tamellar ridges fully sepaarted from the margin of the shell.” 
Fine ridges, parallel to the upper margin, indeed, are seen in 
imbecillis, but they exist also in other species of Anodonta, 
more or less distinctly developed, but are extremely hard to 
distinguish. 
The rest of the description of the shell of ohiensis applies 
to several small or young Anodontas, and Conrad and Iérussac 
believe that ohiensis is Proptera levissima (Lea), ’29, to which 
the description, indeed, might also be referred. 
A. ohiensis is thus not identifiable, and the name cannot be 
used, and consequently, also, the application of the generic 
