THE FAMILY OP UKIONID^. SlU 



wise to elevate each of the peculiar sorts we have mentioned, and many more, into 

 distinct genera, it will be positively necessary to unite them altogether under one 

 generic appellation." 



Deshayes, in his edition of Lamarck's Animmix sans Yertebres, says it is impos- 

 sible to separate the genera of the Umonidce. "]!^ons pourrions prendre pour exemple 

 celui des genres qui est eonsidere comme I'un des mieux caraeterises. Le genre 

 Sympliynote {Lea) est fonde sur ce caractere remarquable que les deux valves sont 

 soudees entre elles le long du bord superieur," etc. "JSTous concluons que tout ce 

 grand ensemble ne pent et ne doit former qu'un seul genre constituant a lui seul la 

 famille des JSfayades."^ 



In his admirable work Traite EUmentaire de ConcJiyliologie, not yet finished, he 

 continues to consider that his twenty-fifth Family, Nayades, is filled by one genus, 

 viz., Unio of Retzius. He makes, however, four divisions, which, he says,^ "diifere 

 a peine de celle de M. Lea." 



I jj • j TInio j A. Sympliynotes. 



I ' " ' ( Hyria I B. Non-symphynotes. 



\ ,^ ., (A. Esp^ces symphynotes. 



„ \Marqaritana ....■{ ^ -^ ^ . ^ i- j 



trenre / ^^- Jispeces non-symphynotes. 



Unio^ Eetzius \Dipsas Sympliynotes. 



\ , 7 , J , , , J A. Esp^ces sympliynotes. 



\ I T -T / -D. Especes non-symphynotes. 



\ '^ Iridina ^ ^ j r j 



It might be exj)ected that some attempt of the application of M'Leay's circular 

 system should be made in regard to this family. Swainson says that "the progres- 

 sion of every natural series is in a circle."^ In my attempts to verify this, I have 



^ Vol. vi. p. 526. — I shall be excused in taking this opportunity to correct an erroneous impression 

 on the mind of M. Deshayes. He says that I was not able to examine the collection of the Museum of 

 Paris. " Malgre cette imperfection qu'il ne pouvait empecher, le travail de M. Lea se recommende a 

 I'attention des naturalistes par ces observations judicieuses, des descriptions exactes," etc. It would be 

 strange, indeed, if, after spending so many years in the study of this familj^, that I should neglect, while 

 in Paris, to see the collections from which Lamarck made so many descriptions. I was frequently at the 

 Museum, and on one particular occasion, by appointment of MM. Blainville and Ferussac, arranged, in 

 the presence of these and other gentlemen, all the species of the Unionidas that were in the Museum, and 

 named them ; and also presented to the Museum about fifteen species which were new to that great 

 national institution. I also did the same thing for Baron Ferussac, having designated every specimen in 

 his cabinet belonging to this famil3% 



* Traile Mem., vol. ii. p. 213. 



" Swainson, in Lard. Cyd. Nat. Hint.., p. 24Y. In his Treatise on Malacology the same author keeps 

 this idea in constant view, and thus invalidates his groups. Besides, he was little acquainted with foreign 

 species. 

 D 



