LEA ON THE GENUS ACOST^A OF D'ORBIGNY. 131 



observed that it is evident the " talon " has been broken off. The drawing represents 

 a fractured portion of this remarkable talon, and I do not feel that it is hazarding 

 much to say, that I have little doubt but the specimen from which the drawing was 

 made, had, in its native bed, a perfect young Naiad at its extended point. 



Should it prove hereafter that MuUeria and Acosicea form one genus, as I certainly 

 believe they do, but two distinct species, of which I have some doubt, it will be 

 necessary to give to Ferussac's shell a specific name, and nothing could be more 

 appropriate than to affix to it that of the distinguished naturalist himself, who first 

 detected it. The genus would then consist of MuUeria Ferussacii and MuUeria 

 Giiaduasana, retaining, of course, the specific name given by the eminent author, 

 M. D'Orbigny. 



