396 ON LAMARCK S FAMILY 



change, as to convince the observer of their identity of spe- 

 cies ; but if any two, near the opposite extremes of arrange- 

 ment, be compared, they would be considered as specifically 

 different. 



De Blainville, a celebrated conchological anatomist, in the 

 second edition of his "Manuel de Malacologie et de Conchili- 

 ologie," p. 539, says, that the animal of the Unio is precisely 

 like that of the Jlnodonta : his words are, " Animal cntiere- 

 ment semhlable a celui des anodontes." It has not been disco- 

 vered that the animal of the Jllasmodonta differs in any 

 respect from those of the Unto and Jlnodonta. 



Under the genus Unio, De Blainville cites Hyria corrugata 

 of Lamarck, as the example of his variety A of Unio : his 

 words are — A. Especes obliques, dont le corselet est dilate et 

 releve en crete saillante, ce qui les rend corame auriculees 

 ou aviculaires. He also cites Castalia ambigua* of Lamarck 

 as the example of his variety C of Unio. It is therefore evi- 

 dent that De Blainville believes the animals of Unio, Hyria, 

 and Castalia, to be identical. 



In the same manner, under the genus Jlnodonta, he cites 

 Iridina exotica of Lamarck as the example of variety A ; 

 and Dipsas of Leach as the example of variety E of Ano- 

 donta. Thus it appears that De Blainville considers Unio, 

 Hyria, and Castalia to be varieties of one genus, namely 

 Unio ; and Jlnodonta, Iridina, and Dipsas to be varieties of 

 one genus, namely Jlnodonta : and since he expressly declares 

 the animals of Unio and Jlnodonta to be identical, may we 

 not safely include the whole six under one genus? 



We may also add Mr Say's genus Alasmodontaf, as no- 

 thing has been discovered in the animal to distinguish it 

 from that of Unio ; and as the structure of its hinge proves it 

 to be the connecting link between Unio and Jlnodonta. 



If the above mentioned seven genera are to be considered 

 as permanent, there are strong reasons why another should 

 be added to them, conformably to a suggestion contained in 



* Possibly, Unio triangularis of Barnes. 



t Is not Masmodonta arcuata of Say identical with Unio sinuata of Lamarck ? 



