46 



VI. SUBGENUS DIPSAS. 



TRIANGULAR. 



*plicatus. ' Leach. 



Barbata plicata. 2 Humph. 

 Myt. plicatus. Soland. 

 Myt. dubius. Chnel. Dill. 

 Cristaria tuberculata. Schum. 

 An. dipsas. Blain. Fer. 

 An. tuberculatus. Fer. 

 An. alatus. Sow. 

 Symph. bi-alata. 3 Lea. Trans. Am. 

 P. S. 



p4 f TRIANGULAR. 



Unio bi-alata. Desk. 

 £ I Dianisolis Qhinensis. 



Raf. 



OVAL. 



*discoideus." Lea. 



Symp. discoidea. Lea, Trans. Am. 



P. S. 

 Unio tenuis. Gray. 5 

 An. tenuis. Gray. 5 

 An. Chinensis. Pkili. 



1 Perfect specimens show the whole linear tooth, and the folds on the posterior slope and on the posterior 

 wing, but old and imperfect specimens sometimes exhibit neither. The imperfect figure and description by Leach 

 (who made the genus in 1815) 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. 



2 Fide Gray. 



3 Mr. Rafinesque, in the continuation of his Monograph (p. 7), affirms decidedly that the Symphynota bi-alata, 

 Lea, is a peculiar genus, but he changes it to Dianisolis Chinensis! ! 



4 The posterior termination of the tooth shows some disposition to duplication, and evidently inclines to pass 

 into the subgenus Unio. 



5 In Griffith's Cuvier. 



