FAMILY NAIADES. 



GENUS MARGARON. 

 I. SUBGENUS TRIQUETRA. 1 



All the species preceded by an * are in my Cabinet. The inner column forma the Synonyms. 



H 



E- 



H 



I 



TRIANGULAR. 



*corrugata. Zara. 



Hyria corrwjata. Lam. Sow. Chenu. 

 ITyria rwjosa. Cuv. 

 Hyria rosea. Lefev. Pot. 

 Hyria transversa. Hupe. 

 Tellina rosea. Bonh. 

 Mya angulata. Wood. 

 Unio rugosus. Wagner. 

 Paxyodon ponderosus. Schum. 

 Triplodon rugosum. Spix. 



*subviridis. Klein. 



Mya syrmatophora. Gronovius. Omel. 

 Wood. Dill. Schreib. Schrot. 



TRIANGULAR. 



Hyria avicularis. 



Crouch. Desk. 



Han. 

 Hyria syrmatophora. Sow. 



Schom. Swain. Hupe. 

 Unio corrugata. Blain.* 

 Hyria elongata?* Swain. 

 Hyria cordata. Menke. 

 Hyria complanata. Hupe. 

 Hyria Castelnauii. Hupe. 

 Unio caudatus. Wagner. 

 Unio syrmatophora. Desk. 

 Prisodon obliquus. Schum. 

 Diplodon furcatum. Spix. 



Lam. Chill. 

 Guerin. Chenu. 



Cuv. 

 Han. 



1 The shell known to zoologists generally as Hyria corrugata, Lam., was long before placed by KU-in 

 under the generic name of Triquetra (Tentamen Metfwdi, 1753, p. 135, PL 9, Fig. 36), and Ferussac 

 adopted it, very properly, in preference to Hyria. In my former editions, I placed Hyria in the subgenus 

 Unio, but the animal has been found to possess two syphons, which ought, with other obvious differeiKv-. 

 to separate it from Unio (Gray, Annals of Nat. Hist., Dec. 1840). Troschel, in Wiegmann's Archi*-'*, 

 describes the soft parts and the cicatrices. The cicatrices in the H. corrugata, he sa3 - s, differ; which is 

 true, as in the genus Hyria there exists iisually a very well marked cicatrix, which is deeply impressed, 

 distinct, and lies over the great anterior adductor cicatrix. He also says that the l~nii> ili'tphinus belongs 

 to this genus, as well as a new shell, Hyria humilis, from Guiana, described by him. 



2 The figure of Blainville, pi. 67, fig. 1, is evidently the smooth Triqm'lra, and no doubt is subririili.*. 

 * Mr. Gray thinks this is a " perfectly distinct species." I have never seen the shell, and feel too 



much in doubt to insert it as such. v 



