THE FAMILY OF UlflONIDJ. Xlll 



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 Animaux sans Vertebres, says it is impos- 

 sible to separate the genera of the Unionidai. "Nous pourrions prendre pour exemple 

 celui des genres qui est considere comme l'un des mieux caracterises. Le genre 

 Sympkynote (Lea) est fonde sur ce caractere remarquable que les deux valves sont 

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

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

 famille des JVayades." 1 



In his admirable work Traite JElementaire 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, 2 "differe 

 a peine de celle de M. Lea." 



j~ ■ I Unio j A. Symphynotes. 



( Hyria ( B. Non-symphynotes. 



\ , r . A (A. Especes symphynotes. 



Margaritana . . . . i _. _, r . j r j 



(jenre ( B. Especes non-symphynotes. 



Unio, Retzius Dipsas Symphynotes. 



/ ( Mi/cetopus ( , _, . 



Anodonta Anodonta 1 1^ symphynotes. 



( j . j. IB. EsjDeces non-symjmynotes. 



It might be expected 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." 3 In my attempts to verify this, I have 



1 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 

 l'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 family, 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 Unionidse 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 family. 



2 Traite Mem., vol. ii. p. 213. 



3 Swainson, in Lard. Cycl. Nat. Hist., p. 24V. In his Ti'eatise 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 



