222 R. W. SHUFELDT 



Doubtless, among the Reptilia generally, we will meet with 

 some very interesting variations of the conditions just described, 

 and they are deserving of far more extensive attention at the 

 hands of comparative morphologists than they have received 

 up to the present time. 



CONCLUSIONS 



That the element heretofore generally considered as the 

 'odontoid bone' in the cervical, series of vertebrae in the che- 

 lonians is, in fact, the centrum of the axis or second vertebra 

 of the neck^ — the true odontoid process being present in such 

 species as constitute the genus Amyda and possibly others. 

 That this second or axis vertebra has, for some reason or other, 

 lost its arch, and in some forms only, as in Chelydra, is there 

 any indication of a haemal spine being present. As in other 

 vertebrates, this to some extent aborted second cervical ver- 

 tebra, articulates anteriorly with the atlas, and posteriorly with 

 the third cervical, and is just as much entitled to be con- 

 sidered the axis vertebra as are various semiaborted bones in 

 the skeletons of other vertebrates so considered. For example, 

 to illustrate this point we may select, from a long list of others, 

 the fibula in certain Cervidae, as the red deer (C. elaphus), 

 wherein it has become reduced, distally, to a mere nodule of 

 bone, and, proximally, to a rudimentary osseous style — the two 

 never being united by bone. Nevertheless, anatomists consider 

 these two osseous rudimentary elements in the leg of a deer as 

 being the fibula, and so name and describe it. 



Having proved, then, that the so-called 'odontoid bone' is, 

 in reality, the axis vertebra in the chelonian skeleton, we find 

 that there are nine vertebrae in the cervical series of the skeleton 

 in the chelonians instead of eight, as comparative anatomists 

 have heretofore claimed to be the case. 



