Extracts from the Proceedings of the Academy of Natural Sciences of Philadelphia, of papers, 



By Isaac Lea. 



[Communicated March 13th, I860.] 



Mr. Lea stated that when he made some remarks, a few weeks since, on the 

 Unionidce of the United States, he gave the number of them incorrectly by an 

 inadvertence. He now desired to restate them numerically : 



Unio, 465 species. 



Margaritana, 26 " 



Anodonta, 59 " 



550 

 To these may be added, new species in his cabinet not yet 



described, 30 



580 



And to these may be added, for North America, known to 



inhabit Mexico, Honduras, Central America and 



one in Canada, Unio, 29 



Anodonta, 8 



— 37 



617 

 It will be observed that we have not in North America either of the genern 

 Triquetra, 'Hyria, Lam.,) Prisodon, (Castalia, Lam.,) Monocondylosa, Mycetopus, 

 Byssandonta, or Plagiodon. They are all emphatically South American types, 

 while there does not seem to inhabit the southern half of America a single 

 species of Margaritana, (Alasmodonla, Say.) Ferussac has described a species 

 (A. incurva) as coming from South America, but there is reasonable doubt of 

 it. The Monocondylosa and Margaritana seem mutually to replace each other. 

 The Uniones and Anodonta prevail in both parts of the continent over all the 

 other genera, both as to numbers and universality of distribution. The genu? 

 MuUeria, (Acostea, D'Orb.) has only been found in the tributaries of the Magj 

 dalena in New Granada. 





