442 NEW GENUS AND SOME NEW SPECIES 



Remarks. — This species approaches closely to the scaknia 

 of Rafinesque ; its rays are of the same description, and the 

 general form is the same. It is, however, more flattened, has 

 much less elevated beaks, and its diameter is alw^ays much less. 

 Its beaks are generally but little decorticated, and not recurv- 

 ed ; the scaknia is generally much recurved and decorticated. 



GENUS SYMPHYNOTA. 



Testa fluviatili, bivalvi ; valvulis superne connatis. 



Shell fluviatile, bivalve ; valves connate at the dorsal margin. 



Animal same as that of Unio. 



Remarks. — Objections will most likely be m.ade to the in- 

 troduction of a new genus into a family acknowledged already 

 to be in great confusion, and presenting many and various 

 difficulties. The formation of the genus Symphynotu, it is 

 hoped, will rather be conducive to a diminution of that diffi- 

 culty, by a division which all must acknowledge to be as na- 

 tural as any of those of the family. The distinctive charac- 

 teristic of this genus is the testaceous connection of the two 

 valves of the shell above the hinge. I therefore remove from 

 the existing genera all the connate shells without regard to 

 the forms of their teeth, believing, that should this family be 

 hereafter remodelled, it will present only two natural genera ; 

 one having a testaceous connection of the valves, the other 

 dispossessed of it. The difficulties attending the adopted ge- 

 nera of the Naiades, viz. Unio of Bruguiere, Hyria, Ana- 

 donta, Iridina, Castalia* of Lamarck, Dipsas of Leach, and 



* This genus was placed by Lamarck in the family Trigonaa, certainly with 

 no propriety. It has been placed by Sowerby and Latreille among the Naiades, 



