NORTH AMERICAN TESTUDINATA. 



CHAPTER FIRST. 



THE ORDER OF TESTUDINATA; ITS RANK, CLASSIFICATION, AND 



GENERAL CHARACTERS. 



SECTION I. 



RANK OF THE TESTUDINATA. 



The necessity of reviewing critically the North American Testudinata,^ in order 

 to obtain a well-founded standard of comparison between the successive changes 

 in the development of those species whose embryology I have examined, and the 

 full-grown representatives of the types inhabiting the continent of North America, 

 affords me a welcome opportunity of testing the principles of classification discussed 

 in the first part of this work. It will be seen from this examination that, though 

 their systematic arrangement requires here and thei'e considerable modifications, 

 yet the progress of science during this century has been such, that the changes 

 I propose to introduce in the most generally adopted classification of the Testu- 

 dinata are sometimes only confirmations of modifications already hinted at by pre- 

 vious writers, whose opinions have not been sustained from want of satisfactory 



* The Tiame Testudinata being older than that desirable to discard it altogether from our illustrations, 



of Chelonians, and yet entirely synonymous with it, I shall therefore still use it whenever this group is 



I deem it necessary to retain it in future as the sys- contrasted with the Saurians and Ophidians, as they 



temiitic name of this order. The name Chelonians were named together, according to the same prin- 



is, however, so generally adopted, that it may not be ciple. 



