676 



REPTILIA. 



Fig. 331. 



skeleton than any other with which we are acquainted : we therefore beg 

 the attention of the student while we investigate this important piece 

 of osteology. 



(1880.) A glance at the skeleton of the Crocodile (fig. 331) at once 

 shows us that, in consequence of the addition of a thorax, and the con- 

 nexion which now necessarily exists 

 between the pelvis and the spine, the 

 vertebral column becomes divisible into 

 distinct regions : viz. the cervical, con- 

 taining seven vertebrae; the dorsal, 

 formed by those vertebrae which support 

 the thoracic ribs ; and the lumbar ver- 

 tebra intervening between these and 

 the sacrum. The number of bones 

 entering into the composition of the 

 sacrum, that is, which are connected 

 with the ossa ilii of the pelvis, are in 

 this case two in number ; while, behind 

 these, six-and-thirty vertebrae enter 

 into the composition of the tail. 



(1881.) In the cervical, dorsal, lum- 

 bar, and sacral regions, no inferior 

 spinous processes exist; but in the 

 caudal portion of the vertebral column 

 these elements are found greatly de- 

 veloped, as in fishes, and obviously with 

 the same intention, namely to increase 

 as much as possible the vertical extent 

 of the tail, and thus convert this part 

 of the body, which is here of extraordi- 

 nary length and great flexibility, into a 

 powerful instrument of propulsion. 



(1882.) The transverse processes of 

 the cervical vertebrae are remarkably 

 large, and so extended that they ma- 

 terially interfere with the lateral move- 

 ments of the neck, an arrangement 

 evidently designed to afford a sufficient 

 extent of insertion for the powerful 

 muscles of the cervical region. 



(1883.) The thorax is composed of a 

 sternum and two sets of ribs, one set 

 being articulated with the transverse processes of the dorsal vertebra, 

 and hence caUed dorsal ribs, while the others, being fixed to the sides 

 of the sternum, are named sternal ribs : the contiguous extremities of 



