Occasional Papers of the Museum of Zoology 37 



This species has become the type of Lasmigona by eHmina- 

 tion of the other species mentioned by Rafinesque {Alasmi- 

 donta maf'ginata Say), as first pointed out by Simpson. 



Anodonta imbEcillis Say, 1829 



Type locality: Wabash River. 



Anodonta (Lastetui) ohiensis Rafinesque, '20, p. 50. 

 Anodonta imbecUis Say, Walker, '18^, p. 176. 



U. IcEvissimus (Lea) =An. ohiensis Raf., Conrad, '34, p. 70; Ferus- 

 sac, '35, p. 25. 



Anodonta imbecillis Say, Simpson, '14, 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 A. ohiensis 

 Raf. that supports the assumption that it is the well-known A. 

 imbecillis Say. In fact, the most striking character of imbe- 

 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, 

 "Lamellar 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 iVnodontas, and Conrad and Ferussac 

 believe that ohiensis is Proptera Iccvissima (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 



