28 



SYNOPSIS OF 



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OBOVATE. 



*Paicliappii. Lea. 

 Moiioc. Paicliappii. 



DOrb. 



*Coiiientesensis. Lea. 



Monoc. Conieiitesensis. jyOrh. 



*Guarayana. Lea. 



Monoc. Guaiayana. D'Orb. 



*fossiculifeia. Lea. 



Monoc. fossiculifeia. D'Orb. 



Minuana. Lea. 

 Monoc. Miuuana. 



D'Orb. 



ARCUATE. 



*maigantifeia. Lea. 



Mya margaritifera. Lin. Chem. 

 Knorr. Dill. Desk. Wood. 

 Mat. Monta. Miihl. Retz. Ml. 

 Margatitana fluviatilis. Sclmni. 

 Unio elongata. Lam. Mich. Bouil. 

 Unio sinuata. Pfeif. 

 Unio Roissyi. Mich. 

 Unio margaritiferus. Pfeif. Drap. 



Turt. 

 Unio livalis. Zeis- 

 Alas, margaritifeiiim. 

 Alas, arcuata. Bar. 



*Holstonia. Lea. 

 *fabula. Lea. 



Flem. 



The following species are unknown to me : 

 Alasmodonia Tiipolilaua. Fer. 

 Alasmodonla incurva. Fer. 



H 



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Z 



S 



m 



III. SUBGENUS DIPSAS. 



TRIANGULAR. 



*plicatus.f Leach. 



Baibata plicata.| Humph. 



Myt. plicatiis. Soland. 



Myt. dubiiis. Gmel. Dill. 



Ciistaria tuberculata. Schum. 



An. dipsas. Blain. Fer. 



An. tubeiculalus. Fer. 



An. alatiis. Soie. 



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



P. S. 

 Unio bi-alala. Desh. 



fOVAL. 



*discoideus.§ Lea. 



Symp. discoidea. Lea, Trans. Am. 



P. S. 

 Unio tenuis. Gray.\\ 

 An. tenuis. Gray. 1| 



the sixth one I place here with some hesitation, as to its proper situation, never having seen it. It is certainly 

 a most interesting group, and it is to be regretted that we have no description of the animal. 



t 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 of this fine shell, led me to believe that it could not be the same wiih that which I described under the 

 name of Sym. bi-alata. 



X On the authority of Gray. 



§ The posterior termination of the tooth shows some disposition to duplication, and evidently inclinee to pass 

 into the subgenus Unio. 



II In Griffith's Cuvier. 



