542 Mr. Lea on the Naiades. 



sion into species should be retained, if it were only for the sake 

 of system." 



If they are not species but varieties, and are to be called so 

 only for system's sake, why say that Lamarck is in error for 

 having done the same thing 1 But where are the proofs of La- 

 marck's errors 1 That eminent conchologist has described forty- 

 eight species of Unio ; twenty-two of these are American, and 

 five are without liabitats. He is constantly receiving shells from 

 the four quarters of the globe, and how can Mr. Lea, who has 

 not the examples before him, assert that he is in error ? Since, 

 however, Mr. Lea does not scruple to criticise one whom he calls 

 accurate, he may well consent to have the number of his disco- 

 veries among these mazes and insensible gradations, reduced at 

 least one half. I shall venture to apply this restriction to an 

 enumeration of fifty -one species by name, which at page 172 of 

 the review, Mr. Lea is stated to have added. Giving him the 

 advantage of the odd number, and calling the number twenty- 

 six, I shall state without hesitation that twejity-Jive of that num- 

 ber have been previously described by other conchologists ; these 

 are the Unio occidens, U. orietis, U. trapezoides, U. multipUcatus, U. 

 ellipsis, U. irroratus, U. planulalus, U. pustulosus, U. pustidalus, U. 

 soleniformis, U. pcrplexus, U. parvus, U. pileus, U. .Xsopus, U. sulca- 

 tus, U. pyramidatus, U. lacrymosus, U. asperrimus, U. brevidens, U. 

 varicosus, U. circiihts, U. patulus, U. rubiginosus, U. donaciformis, 

 U. securis. 



It would be too tedious a task to give all the details which be- 

 long to this extensive piece of " 7iice disa'imination ;" the inspec- 

 tion of numerous collections, including his own, would be neces- 

 sary to the complete establishment of the fact. My own opinion 

 is grounded upon actual comparison, and I here express it as my 

 belief, in a deliberate manner. I shall nevertheless give some 

 of the grounds for it, which will perhaps gain me credit for what 

 at present I can only assert. Before these details are entered 

 upon, it may be as well to examine what Mr. Lea's claims are 

 to that character for " extent and nicely of disa-imination" which 

 his eulogist claims for him. In doing this, perhaps, we shall find 

 the measure of discrimination possessed also by his eulogist. At 

 page 173 it is said, "with respect to Mr. Lea's distribution of the 

 naiades into the two genera Unio and Symphynola, — the distinc- 

 tive character for the former being valves free, and for the latter. 



