1/4 BULLETIN OF THE NEW YORK STATE MUSEUM 



Anodonta undulata, Say 

 Anodonta subcylindracea, Lea 

 Anodonta implicata, Sav 



Anodonta fluviatilis, Dillw. 

 Anodonta Lewisii, Lea 



The resemblance between the beaks of U. pressus, Lea, 

 and U. Tappanianus, Lea; between U. luteolus, Lam., and 

 U. radiatus, Lam.; between U. ockraceus, Say, and U. cario- 

 sus, Say, supported by resemblances between other charac- 

 ters of the shells seems to warrant the supposition that the 

 two members of each pair are closely related. The beaks of 

 U. nasutus, Say, resemble in some measure those of U. 

 radiatus, Lam., but the two shells have very little resem- 

 blance in other specific characters. U. complanatus, Solander, 

 differs both in beak and other characters, from the other 

 Unios of the vicinity. 



Among the Margaritanse of this neighborhood a distinct 

 relationship exists between the beaks of M. marginata and 

 M. rtigosa, and in the adult state these two species are more 

 or less related because of the corrugations on the posterior 

 dorsal area. M. undulata, Say, in its beak characters differs 

 greatly from both of the preceding species, but there is no 

 close resemblance in other features existing between the 

 latter and the two former which would lead one to anticipate 

 a corresponding resemblance of beaks. 



Among the Anodontse a slight resemblance exists between 

 the beaks of An. undulata, Say, and A71. subcylindracea, Lea, 

 but the resemblance is not at all marked. A marked 

 relationship exists between An. fluviatilis, Dillw., and A n. 

 Lewisii, Lea, both in beak and other characters. According 

 to some of its conchological features, An. implicata, Say, is 

 related to An. fluviatilis, Dillw., but the undulations of the 

 beaks of the two species differ materially. 



By far the greater portion of the material used in the prep- 

 aration of this paper was drawn from the collection of 



