FAMILY ^klAJ)ES.— Lamarck. 



.GENUS MARGAEON. 

 I. SUBGENUS TRIQUETRA.' 



All the species preceded by an * are in my Cabinet. The inner column forms the SjTionyms. 



TRIANGULAR. 



*corrugata. Lam. 



Hyria corrugata. Lam. Sow. Chenu. 

 Hyria rugosa. Cuv. 

 Hyria rosea. Lefev. Pot. 

 Hyria transversa. HupL 

 Tellina rosea. JBonh. 

 Mya angulata. Wood. 

 Unio rugosus. Wagner. 

 Paxyodon ponderosus. Schum. 

 Triplodon rugosum. Spix. 



i1 



*su'bviridis. Klein. 



Mya syrmatophora. Gronovius. Omel. 

 Wood. Dill. Schreib. Schrot. 







TEIAKGULAE. 









Hyria avicularis. Lam. 



Child. 







Crouch. Desk. Giierin. 



Chemi 



< 





Han. 









Hyria syrmatophora. Soiv. 



Cuv. 



<3 





Schom. Swain. Hupe. 



Han. 



g 



a 



Unio corrugata. Blain.'^ 





&5 ■ 



1 ■ 



Hyria elongataP Swain. 





O 



a ■ 



s 



Hyria cordata. Menlce. 









Hyria complanata. Hupe. 









Hyria Gastelnauii. Hupe. 









Unio caudatus. Wagner. 

 Unio syrmatophora. Desh. 

 Prisodon oiliquus. Schum. 

 Diplodon fureatum. Spix. 





' The shell known to zoologists generally as Hyria corrugata, Lam., was long before placed by Klein 

 imder the generic name of Triquetra (Tentamen Methodi, 1753, p. 135, PI. 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 differences, 

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

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

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

 distinct, and lies over the great anterior adductor cicatrix. He also says that the Unio delphinus belongs 

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



' The figure of Blainville, pi. 61, fig. 1, is evidently the smooth Triquetra, and no doubt is subviridis. 



' 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. 



