206 OK THE NATADES, 



it comes only from the more southern rivers of South America. My 

 specimens, and those I saw in Europe, came from the river La Plata. 

 It has a peculiar character, which Lamarck does not notice, in the 

 deposit of epidermal matter at different stages of growth, with the nacre 

 extending in waved lines, generally from one great cicatrix to the other, 

 forming curves parallel with the palleal cicatrix. 



iAnodonta glauca is a distinct species, inhabiting Mexico, and figured 

 in a recent number of Humboldt's great work. 



Anodonta sinuosa. I saw the specimen described, in Baron de 

 Ferussac's cabinet. It is very distinct, and very peculiar in the sinuous 

 dorsal line. This species is in my cabinet, 



Jlnodonta Patagonica. This is also a distinct and very rare species. 

 The possession of a specimen I owe to the kindness of Mr G. B. 

 Sowerby. 



Iridina exotica. To Baron de Ferussac I owe the possession of this 

 species. It appears to differ from the Nilotica in being tuberctdated 

 along the dorsal line, which is one of Lamarck's generic characters. 

 The Nilotica, which I received from the African traveller Monsieur 

 Cailliaud, has no crenulations along the dorsal line, but I have seen 

 specimens on which a few could be observed. The Clappertoni of 

 Denman is a young Nilotica. 



