Dr. J. E. Gray on American Emydidse. 1 77 



many young of E. ornata I have seen; and, like that species,. it 

 is a Trachemys, and not a Ptychemxjs of Agassiz. Both E. ve- 

 nusta and E. callirostris, which the Professor believes to be only 

 varieties of his Ptychemys concinna, are also species (and, I be- 

 lieve, most distinct ones) of his genus Trachemys. 



As to Emys mobilensis and E. ventricosa being the same, this 

 is only a repetition of the statement I have made in the Cata- 

 logue ; but this is the case with many other observations which he 

 puts forward as his own, rather than copies of my own corrections. 

 But, as I only knew one species from a shell without any ani- 

 mal, and the other from the figure in Dr. Holbrookes work, I 

 considered it better to let them remain for further examination. 

 Here, again. Professor Agassiz has never seen the original spe- 

 cimen on which E. ventricosa is founded. 



The same observation is applicable to the proposed union of 

 E. rivulata and Pseudemys serrata. The former is described 

 from a shell without an animal ; and it is so very unlike any 

 specimen of Pseudemys serrata that I have seen, that I think it 

 is very unsafe to unite them without further evidence. 



This analysis will show how fallacious is the argument that 

 the genus " Pseudemys is not well founded, as the two species 

 which he himself had the opportunity of examining are only 

 varieties of other species which he refers to the old genus Emys'* 

 I may first observe that the genus Pseudemys is separated from 

 Emys by the form of the lower jaw and beak, and the scales 

 and size of the web of the feet — characters only to be seen on 

 the animal (so that my referring Emys ventricosa and E. rivu- 

 lata to species described from shells alone, without any part 

 of the animal attached to them, is no proof as cited) ; secondly, 

 that E. ornata, E. venusta, E. callirostris, and E. annulifera, 

 which are founded on perfect specimens, have proved, on exa- 

 mination, not to belong to my genus Pseudemys or M. Agassiz^s 

 genus Ptychemys ; and thirdly, that E. floridana and E. mobi- 

 lensis are only placed in the Catalogue on the authority of the 

 figures and description of Dr. Holbrook, — all proving that the 

 Professor^s observations are not well founded. I might as well 

 say that his genera Ptychemys and Trachemys are not well 

 founded ; for he regards E. ornata, E. venusta, E. callirostris, and 

 E. annulifera, from the examination of the figures or descriptions 

 alone, as varieties of Ptychemys concinna, when they are, in fact, 

 species of his genus Trachemys, which would, according to his 

 argument, prove that these genera are not distinct ! 



But further, I have no doubt that Professor Agassiz will admit 

 that Pseudemys is well founded, when he finds that it and his 

 genus Ptychemys are synonyms of one another, founded on 

 nearly the same characters and on the same species, my characters 



