THE FAMILY NAIADES. 3 



prising that authors who having only met with certain species, 

 and not being aware of such intermediate links, should have 

 considered them as the types of new genera."* And further, 

 " we think we have already said enough to prove, that unless 

 it be thought 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." Swainson (Zool. Illus. second series,) 

 divides this family into Unio, Hyria, Iridina, Jlnodon, and 

 Masmodon, but in describing An. ariolatus speaks of the 

 genera gliding into each other. 



Deshayes, in his edition of " Lamarck's Animaux sans Ver- 

 tebres," says it is impossible to separate the genera of the 

 Naiades. " Nous pourrions prendre pour exemple celui des 

 genres qui est consider^ comme Fun des mieux caracteris6s. 

 Le genre symphynote est fonde sur ce caractere remarkable 

 que les deux valves sont soudees entre elles le long du bord 

 superieur," etc. " Nous concluons que tout ce grand ensem- 

 ble ne pent et ne doit former qu'un suel genre constituent a 

 lui seul la famille des Nayades.^'^ 



* Zoolog. Jour. Vol. I. 



■\ Vol. VI. p. 526. — I will be excused in taking this opportunity to correct 

 an erroneous impression on the mind of M. Deshayes. He says I was not 

 able to examine the collection of the museum of Paris. " Malgre cette imper- 

 fection qu'il ne pouvoit empecher, le travail de M. Lea se recommende a I'at- 

 tention des naturalistes par ces observationes 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 col- 

 lection from which Lamarck made so many descriptions. I was frequently at 

 the museum, and on one particular occasion, by appointment of MM. Blain- 

 ville and Ferussac, arranged in the presence of these and other gentlemen all 

 the species of the JVaiades that were in the museum, and named them ; and 

 also presented to the museum about fifteen species which were not there. I 

 also did the same thing for Baron Ferussac, having designated every specimen 

 in his cabinet belonging to this family. 



