570 



BEPTILIA 



[CH. 



to the front end of the centrum (ventral intercalary) behind the 

 basiventral to which it belongs. The tubercular attachment is 

 represented by ligament. There are two sacral vertebrae which 

 have expanded transverse processes with which the ribs are fused. 

 Behind these come the vertebrae of the tail the caudal vertebrae. 

 Each of these bones is made up of two halves, an anterior and a 

 posterior, which are but loosely connected with one another. The 



consequence is that when a lizard 

 is seized by the tail this organ in 

 many species snaps in two, one of 

 the vertebrae breaking into an an- 

 terior and a posterior half. 



All vertebrae in front of the 

 sacrum, except the first two, have 

 distinct ribs attached to their 

 transverse processes. In young 

 specimens it can be seen that the 

 odontoid process is separated from 

 the second centrum, with which 

 it ultimately fuses, by a cartilagi- 

 nous pad representing the second 

 pair of basiventrals, the first pair 

 of basiventrals forming, as has 

 already been explained, the ven- 

 tral portion of the atlas verte- 

 bra, to be separated from the 

 centrum of the second vertebra 

 by an unossified disc representing 

 the second pair of basiventrals 

 (Fig. 278). 



The ribs in front of the pec- 

 toral girdle remain quite short ; 

 this region is the cervical or neck 

 region. Immediately behind the 

 pectoral girdle the ribs are very long and curved so as to half 

 encircle the body like the hoops of a barrel. The foremost have 

 attached to their lower ends cartilaginous bars termed the sternal 

 ribs, which are in turn united with a cartilaginous sternum in the 

 middle line. This structure has the form of a lozenge-shaped plate 

 with a hole in the middle, ending behind in two forks to which some 

 of the posterior sternal ribs are attached. The front portion of the 



FIG. 280. Ventral view of the 

 shoulder-girdle and sternum of 

 a Lizard, Loernanctus longipes 

 x2. After Parker. 



1. Interclavicle. 2. Clavicle. 

 3. Scapula. 4. Coracoid. 



5. Precoracoidal process. 6. Glen- 

 oid cavity. 7. Sternum. 



8. Sternal bands not united. 



9. Sternal rib. 



