198 ON THE NAIADES, 



umbonial slope near to the margin, the edges of each growth being there 

 dentate. In some specimens this is so strongly marked as to resemble 

 a thick cord. The drcseformh, professor T. doubts being in Tennessee 

 river. He found it only in the Cumberland. He was, I believe, the 

 first person who sent this species to New York and this city. Some 

 fine old specimens, recently received from that gentleman, exhibit a 

 diameter of a most extraordinary nature, as well also an almost perfect 

 flatness of the posterior slope. My oldest specimen, when placed on 

 a plane, will rest both on the base and on that slope. The specimen 

 figured by me, was not more than two-thirds grown, and was then the 

 best specimen I had seen, and I supposed it to be an adult. 



OBSERVATIONS ON LAMARCK'S NAIADES. 



Having had the opportunity while in Paris recently, to inspect most 

 of the cabinets to which Lamarck refers in his description of the 

 Naiades, I seized the opportunity to examine the individual specimens 

 from which he made his descriptions ; and having made notes on the 

 spot, I feel great confidence as to the facts, and trust that my judgment 

 as to the decisions on his species will be found to be correct. 



In pointing out the errors of this great zoologist, we must not be 

 astonished at their number, nor should the slightest shadow fall upon 

 his merited and exalted reputation. We should rather think of the 

 means within his power, the poverty of the materials with which he 

 worked, and above all, the unfortunate ophthalmia which afflicted his 

 declining years, and which he deplores in the advertisement of the 

 sixth volume of his Hist. Nat. des Animaux sans Vertebres. 



Unio sinuata. This is a true species, but Klein is entitled to the 

 name which he gave first to it, viz. crassissima.* It has been consi- 

 dered by the conchologists of this country (and I certainly was of the 



* See Transactions of the Linnean Society of Bourdeaux, Vol. II. p. 42. 



