THE FAMILY NAIADES. 



47 



SUBGENUS DIPWAS. 



P 

 < 



O 



TRIANGULAR. 



plicatus.* Leach. 



Myt. plicatus. Soland. 



Myt. dubius. Grnel. Dill. 



Cristaria tuberculaLi ? Schnrn. 



An, dipsas. Fer. 



An. tubercLilatus. Fer. 



Symp. bi-alata. Lea, Trans. Am, 



Unio bi-alata. Desk. 



P. S. 



o 



OVAL. 



discoideus.t Lea. 



Symp. discoidea. Lea, Trans, Am, P. S. 

 Unio tenuis. Gray.X 

 An. tenuis, Gray.X 



* Perfect specimens show the whole linear tooth, and the folds on the pos- 

 terior slope and on the posterior wing, but old and imperfect specimens some- 

 times exhibit neither. The imperfect figure and description by Leach of this 

 fine shell led me to believe that it could not be the same with that which I 

 described under the name of Sym. bi-alata. 



■}• The posterior termination of the tooth shows some disposition to dupli- 

 cation, and evidently bears a disposition to pass into the subgenus Urdu. 



i In Griffith's Cuvier. 



