49S 



UNIONItfjE. 



Kleinianus, Lea. 

 multiplicatus, Lea. 

 Napeanensis, Conr 

 perplicatus, Conr. 



plicatus, Lesueur. 

 Stewardsonii, Lea. 

 undulatus, Barnes. 



Sub-gen. metaptera, Rafinesque (Proptera, Raf. Lymnadia, 



Megadomus, Sivains.). 



Shell with the hind hinge-margin elevated and winged; the 

 valves connate, the surface plicate or smooth. 



alatus, Say. 

 atromarginatus, Lea. 

 Boykinianus, Lea. 

 Cumingii, Lea. 

 decoratus, Lea. 

 delphinus, Gruner. 

 gigas, Lea. 



gracilis, Barnes. 

 inflatus, Lea. 

 laevissimus, Lea. 

 Nicklinianus, Lea. 

 pressus, Lea. 

 psammoicus, D'Orb. 

 superbus, Lea. 



Genus BYSSANODONTA, D'Orbigny. 



Animal resembling that of Anodonta, but remaining 

 always attached by a byssus. 



Shell sub-rotund, inequilateral; beaks elevated, folded, 

 retuse. Hinge with the cardinal teeth recurved, double in 

 both valves ; the lateral teeth rather long and curved ; 

 ligament thin. 



Syn. Byssodonta, (D'Orb.) Gray. 



Ex. B. Paranensis, D'Orbigny, pi. 117, fig. 1, 1, a. 



This remarkable byssiferous fresh-water bivalve was 

 observed by M. D'Orbigny in the Rio Parana, above 

 Corrientes. 



