A SEGMENT OF THE SKELETON. 



15 



A tolerably complete segment of tlie spinal skeleton may- 

 be studied in tlie antei-ior part of tlie thorax of a crocodile 

 ( Fig. 5). It presents a procoelous vertebral centrum (C), united 

 with which by the neurocentral suture is the neural arch, 

 which rises into the neural spine (N.S.). Two processes, the 

 prezygapophyses {Z), extend from the front part of the arch, 

 and have flat articular surfaces turned dorsally. Two others 

 of similar form, but having their articular surfaces turned 

 ventrally, proceed from the postei'ior face of the neural 

 arch, and are the postzygapophyses {Z'). By these, which are 



I 



Jiti. 



s& 



Sf-f 



Fig. .5. — S. fegment of the endoskeleton in the anterior thoracic region 

 of the body of a Crocodile. — C, the centrum or body of the vertebra ; 

 N. S , the neural spine ; Z, the prezygapophysis ; Z', the postzygapo- 

 physis ; T.f, the transverse process which articulates with the tuber- 

 culum of the rib («) ; Cp.t, that which articulates with the capitulum 

 of the rib(C/)); K.r, the ossified vertebral rib; J. r', the part of 

 the verteiiral ril) which remains cartilaginous ; St.r, the sternal rib ; 

 Sf, an artificially separated segment ot the sternum ; P.a, the unci- 

 nate process. 



often called oblique, or articular, processes, the vertebra 

 articulates with the coi-responding processes of its pre- 

 decessor or successor in the series. The transverse pro- 

 cesses are two on each side, one superior and one inferior. 

 The former {T.t) articulates with the tuberculum of the 

 rib, the latter {Cp.t) with its capituhim. They may, there- 

 fore, be called capitular and tubercular transverse processes 

 respectively. Each rib is divided by an articulation into 



