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



that the evidence I have adduced ia the case of Ptychemys 

 rugosa is sufficient to show that in some types the colour does 

 not afford specific characters. This is the case to the same ex- 

 tent with Ptychemys concinna, which is mentioned under four 

 different names hy Dr. Gray, — as Emys ornata, E. Floridana, 

 E. annuUfera, and Pscudemys concinna. Ptychemys Mobilensis 

 appears twice, as Emys Mobilensis and as E. ventricosa. Ptych- 

 emys rugosa also appears twice, as Emys rivulata and Pscud- 

 emys serrata. These facts are sufficient to show that Gray's 

 genus Pscudemys is not well founded, as the two species which 

 he himself had an opportunity of examining are only varieties 

 of other species, which he refers to the old genus Emys. I am 

 unable to refer his Emys venusta with certainty, as his figure, 

 though well drawn, does not exhibit the generic characters. I 

 believe it, however, to be one of the many varieties of Ptychemys 

 concinna. The same remark applies to Emys callirostris " 

 (p. 641). 



1 will proceed to examine these observations seriatim. 



I am quite aware, from the examination of living specimens 

 of Emydes, that they change considerably in colour as they 

 increase in age, and under different local or accidental circum- 

 stances ; that is to say, that the colours, which are very distinct 

 and well defined in the young, become more diffused and obscure 

 in the adult ; but at the same time I have also observed that the 

 disposition of the colours does not change, and for that reason, 

 in the Catalogue above referred to, I attempted to divide the 

 species of the genus Emys according to the system of colouring, 

 that is to say, according to the disposition of the coloured rings 

 or streaks, which are best observed in young specimens. It is 

 this which renders the study of the young individual so im- 

 portant, and the want of sufficient attention to it by preceding 

 herpetologists renders their figures and descriptions so difficult 

 to identify; and I think that if Professor Agassiz had paid more 

 attention to it, he would not have proposed to unite under one 

 name species so distinct as those in the observation quoted. 



I will now proceed to the second subject, — that I have men- 

 tioned one species under four names, — from which one would 

 naturally suppose that I had described it four times over, after 

 examination, which is not the case ; for, as far as E. Floridana is 

 concerned, I have only inserted it in the Catalogue on the au- 

 thority of Leconte, Dumeril and Bibron, Holbrook, and Bona- 

 parte, who have all considered it as distinct. When the Cata- 

 logue was published, I had not been able to procure a specimen. 

 As regards Emys annulifera, which is only described from a very 

 young specimen without a habitat, and which may be African or 

 Indian as probably as American, I can only say that I compared it 



