CiiAP. I. RANK OF THE TESTUDINATA. 239 



Now, to return to the question of the natural limitation of Reptiles, it must he 

 obvious that if classes tlifier by the manner in which the plan of their branch is 

 carried out, or by the ways and means employed in framing their structure, we 

 cannot suppose that animals which, like Batrachians, lay a large number of small 

 eggs, the yolk of which is segmented in the well-known manner, to produce an 

 embryo, without amnios and allantois, undergoing extensive metamorphosis after 

 it is hatched, furnished with external gills, which actually perfonn respiratory func- 

 tions, even though they may disappear at a later period of life, the skin of 

 which is naked, etc.,^ belong to the same class as the true Reptiles, the skin 

 of which is covered with horny scales, which lay few, and comparatively large 

 eggs suri'ouuded with a shell, the yolk of Avhich undergoes only a supei-ficial 

 segmentation, and from which is formed an embryo inclosed in an amnios, and 

 afterwards in an allantois, and which, after being hatched, undergoes no mai'ked 

 transfonnation, etc. The conclusion that Batrachians and Reptiles constitute two 

 distinct classes, the first of which is indeed more closely allied to Fishes than to 

 the true Reptiles, is not only of great zoological importance, but has also the 

 most direct bearing upon the question of the order of succession of Vei-tebrates 

 in geological times, and cannot fail to give a new interest to our investigations 

 upon this subject, as well as to increase the precision of our knowledge respecting 

 the first appearance of Reptiles upon earth. 



It will indeed be obvious at once, that if all the so-called Reptiles which have 

 been mentioned as occurring in the carboniferous beds and even in strata below 

 the coal, belong to the class of Batrachians and not to that of genuine Reptiles, 

 the inference to be drawn from the presence of such animals during these ancient 

 geological periods cannot be the same, and instead of leading to the assumption 

 that conditions of existence similar to those which sustain our Reptiles prevailed 

 as far back as these remains are found, we shall only have the evidence that 

 the conditions essential to the life of Batrachians, but not to that of true Reptiles, 

 were established then. 



After this separation of the Batrachians from the true Reptiles, we have only 

 three orders left in the class of Reptiles proper: the Ophidians, the Saurians, and 

 the Chelonians. It would lead me too far from my immediate subject, were I to 

 examine here, whether this is the most natural subdivision of Reptiles into orders. 

 I shall limit myself, therefore, to the consideration of the Chelonians alone, remark- 

 ing only, that whether this division be natural or not, whether we include the 

 Crocodilians in the same order as the true Lizards, or whether we regard them 

 with their fossil representatives as a distinct order, or whether we consider the 



' See further Jetails in any analomiial text-book. 



