576 



REPTILIA 



[CH. 



FIG. 283. Lateral view of the 

 shoulder-girdle of Varanus 

 xf. 



1. Suprascapula. 2. Scapula. 

 3. Glenoid cavity. 4. Co- 

 racoid. 5. Clavicle. 6. In- 

 terclavicle. 7. Precora- 



coidal process. 



bone; this region as in Amphibia is called the suprascapula. 

 Along the inner edge of the suprascapula, scapula and precoracoid 



runs a strong membrane bone, the 

 clavicle, which reaches a median bone, 

 the T-shaped interclavicle. This 

 bone underlies the sternum. The two 

 epicoracoid cartilages join the anterior 

 edges of the sternum (Figs. 280 and 

 283). 



The space between the coracoid 

 and precoracoid is called the coracoid 

 fontanelle. Since in the Urodela it 

 is not closed by an epicoracoid it may 

 be regarded as a bay or indentation in 

 the lower half of the originally simple 

 pectoral girdle. The condition of 

 affairs in Urodela throws considerable 

 light on what occurs in certain other 

 Lacertilia, such as the American 



Iguana. There we find that a similar deep indentation has become 

 developed on the inner side of both scapula and coracoid, so that 

 projections are formed to which the names mesoscapula and 

 mesocoracoid have been given. These are not ossified by sepa- 

 rate bones but are regions of the scapula and coracoid bones. 



The fore-limb of the lizard might be taken as the type of the 

 pentadactyle limb, since there are five fingers and the carpus has 

 all the nine bones developed. 



The pelvic girdle differs markedly from that of any Amphibian, 

 in that in its lower portion there is a hole called the obturator 

 foramen, corresponding to the coracoid foramen in the pectoral 

 girdle. The girdle is ossified by three bones, viz., a vertical ilium 

 articulating with the ribs of the sacral vertebrae, a pubis ossifying 

 the anterior limb of the lower half of the girdle and an ischium 

 ossifying the posterior limb. Both pubis and ischium meet their 

 fellows in the middle line ; such a union is termed a symphysis. 

 The two obturator foramina are closed below and at the same time 

 separated from one another by a longitudinal ligament which may 

 have a certain amount of ossification in it. All three bones con- 

 tribute to the formation of the acetabulum, the cavity for the 

 articulation of the femur. 



We have already pointed out that all Amniota possess a distinct 



