178 Dr. J. E, Gray on American Emydidse. 



being taken from the external part of the beak, and his from the 

 ridges on the palate ; but then Pseudemys has the priority, which 

 may be a grievance. 



Now it is quite evident, from these observations, that Prof. 

 Agassiz has never seen these species, and he must have formed 

 these opinions solely on the sight of the plates and descriptions; 

 and I think that he must have read the latter very cursorily, or 

 else he has not understood the importance of some of the cha- 

 racters there given, or I feel convinced that he could never have 

 committed such a mistake; for certainly his practice, as proved 

 by the paper in which these observations are contained, is not 

 to " lump " species together, but rather the contrary, as is proved 

 by his previous work on Fossil Fish, on Echinida, and even by 

 the work here quoted ; for I must say, after examining a large 

 series of specimens, from different parts of the United States 

 and of different ages, that I cannot agree with him in separating 

 the specimens of Chrysemys, of Cistudo, &c., into several species, 

 as he has done ; and several of the new species indicated (for he 

 promises to describe them in some future work) appear to be 

 separated on very slight characters ; while the species here pro- 

 posed to be combined not only are most distinct, but belong to 

 different genera, according to the characters which he himself 

 used in the family Emydidse for the separation of genera. 



I am much surprised that such an experienced zoologist 

 should have been led to give such a crude opinion, ex cathedra, 

 without first examining the type specimens on which the species 

 were founded, or at least specimens obtained from the same 

 locality, which agreed with the description and figures. 



My experience as a student of Tortoises does not agree with 

 the opinion expressed by Professor Agassiz " that there are 

 genera among our Emydoids in which neither the tint nor the 

 pattern of coloration affords any specific characters" (vol, i. 

 p. 432, foot-note). It is no doubt true that the tint of colouring 

 is not only liable to vary with age, but is also influenced by 

 the peculiarities of the locality, as the purity and clearness, or 

 muddiness, the stillness or current of the water in which they 

 happen to be located ; but as regards the pattern, it is far other- 

 wise. And I cannot think that Professor Agassiz would have 

 made such an observation if he had studied the subject with 

 sufficient care, or even had worked out the observations which 

 I have made on this subject in the Catalogue that he was criti- 

 cising; for he would there have seen that some of the groups 

 which he has called genera are separated and characterized by 

 the pattern of the colour. 



The pattern, to be understood, should be studied in the young 

 animals, and traced up through all the stages until they are full- 



