Dr. J. E. Gray on North American Testudinata. 287 



with young specimens of E. ornata and P. concinna of the same 

 size, and was convinced of its distinctness, and T am certain that if 

 Professor Agassiz had had the same opportunity (which he cannot 

 have had, as the specimen has not been even figured), he would 

 have come to the same conclusion as I have done, — and yet he 

 gives his opinion on the subject ex cathedra without the slightest 

 doubt. If he had compared the system of coloration, as I have 

 done, of Emys ornata, Emys annulifera, and Pseudemys con- 

 cinna in their young state, and E. ornata and P. concinna in 

 their various states of growth, he never could have made such a 

 statement that they were the same species, or have thought it 

 possible that E. venusta and E. callirostris were only varieties of 

 the same. Such random assertions are very injurious to the 

 progress of science, especially when they profess to be made on 

 special and mature study of the subject ; and it is curious that 

 Professor Agassiz, who has figured the young state of many of 

 the North American species, does not appear to have properly 

 estimated the important characters they present, or to have stu- 

 died the manner in which the colouring is modified by the growth 

 of the shields in the difierent species. 



I have nothing to object to the proposal to unite Emys Mo- 

 bilensis to E. ventricosa, except that the statement as made by 

 M. Agassiz conveys a misrepresentation of the facts ; for in the 

 Catalogue, p. 28, under the citation of E, Mobilensis, from Hol- 

 brook, I state, " The figures (Holbrookes) greatly resemble my 

 E. ventricosa, but the margin is represented as having sutural 

 spots, which is not the case in that animal. See No. 25 ;" and 

 under *'25. Emys ventricosa" I quote " t Emys Mobilensis, Hol- 

 brook,^^ as a synonym, and, in the observations, enter into parti- 

 culars showing that they may probably be the same, as Mr. 

 Holbrookes artist is not always accurate in the disposition of 

 the colours of the lower edge of the shells. 



In the Catalogue I make the following observation respect- 

 ing E. rivulata : '^ I describe this species with doubt, as I have 

 only seen a single shell, in its adult state, without the animal ;" 

 and I may observe, that its North American origin is even 

 doubtful. The general form and structure of Emys rivulata is 

 so exceedingly unlike any other Emys, that I was induced to 

 describe it without waiting for other specimens; but since Pro- 

 fessor Agassiz's observations, I have compared it with our nearly 

 adult specimen of Pseudemys serrata, and there is a certain 

 amount of resemblance between them; so that I will not take 

 upon myself to say that they are certainly distinct ; but if they 

 are alike, the Museum specimen is a very remarkable variety. 



I may observe, that as the shell from which the species was 

 described is without its head or skull, and therefore does not 



