166 FOSSIL BIRDS. 



to that of the preserved skeleton of the celebrated Ibis, though 

 evidently not exactly of the same species. 



But all these ideas must be considered as conjectures, and 

 by no means possessing the decided certainty which attaches to 

 the proposition which we have laid down, concerning the bones 

 of quadrupeds. 



It is^ however, a very great point, to have proved the exist- 

 ence of the class of birds among the fossil remains of former 

 worlds ; to have proved that at this remote era, when the 

 species of animals were so different from those which we behold 

 at the present day, the general laws of co-existence, of struc- 

 ture, in short of all which is elevated above simple specific 

 relations, all which belongs to the nature of organs, and to their 

 essential functions, were the same as at present. 



We find, in fact, that when the proportions of the parts, the 

 length of the wings and of the feet, the articulations of the 

 toes, the forms and number of the vertebrae in birds, as well as 

 in quadrupeds, and among the latter, the number, form, and re- 

 spective position of the teeth, are subjected to the great rules 

 established by the nature of things, almost as certain conse- 

 quences are to be deduced from reasoning as from actual ob- 

 servations. 



It is vain, then, any longer to insist on variations of organic 

 structure being the result of habits or circumstances. Nothing 

 has been elongated, shortened, or modified, either by external 

 causes or internal volition ; all that has been changed has been 

 changed suddenly, and has left nothing but wrecks behind it, to 

 advertise us of its former existence. 



Fossil Reptiles. 

 In describing the fossil remains of extinct animals, M. Cuvier 

 found it necessary, in his great work, to give a preliminary and 

 very detailed description of the fossil osteology of the living 

 species. Through this it was not to be expected that we should 

 strictly follow him, as the necessity of so doing has been in some 



