THE RIBS. 59 



THE CORACOID. 



The coracoid is united by suture with the scapula and forms the inferior portion of the 

 glenoid cavity. The anterior and inferior borders of the coracoid are turned inward and describe 

 together a nearly complete semicircle. This border is much thickened at the postero-inferior 

 angle, and this thickening might be considered as indicative of the presence of sternals. 

 There is a rather deep notch between the inferior border of the coracoid and the glenoid 

 cavity. The coracoid foramen is large, and its elliptical internal opening is situated some 

 distance below the coraco-scapular suture and midway between the anterior and posterior 

 borders of the bone. 



THE RIBS. 



Besides the so-called sacral ribs borne by the sacrals in the Ceratopsia all regions of the 

 vertebral column bear ribs. These begin with the axis and continue to the anterior caudals. 

 There are therefore present in the Ceratopsia cervical, dorsal, and caudal ribs. 



THE CERVICAL RIBS. 



All the cervical vertebra? except the atlas [and axis] bear double-headed cervical ribs, as 

 shown in fig. 48. The ribs of the posterior cervicals are longer than those of the anterior, but 

 are straight and not arched, as are the ribs of the dorsal region. They are thin, flat bones, 

 pointed distahy, but at their proximal extremities they branch and form tubercular and 

 capitular processes, the indentation being more marked than in the ribs of the dorsal region. 



THE DORSAL RIBS. 



Commencing with the eighth [ninth] presacral vertebra the ribs assume a different form and 

 position. Instead of being straight and directed backward, as in the cervical region, they are 

 curved with the arch outward and are directed downward, so as to inclose the thorax and to 

 some extent also the abdomen. These are the ribs of the dorsal region. They are all double 

 headed, and in the anterior ribs the tuberculum and capitulum are well separated, as would be 

 expected from the positions of the tubercular and capitular facets, which are situated, respec- 

 tively, on the extremity of the transverse process and the sides of the centra. In the posterior 

 ribs, however, the capitulum is not so far removed from the tuberculum, since in this region of 

 the vertebral column the capitular facet has shifted its position from the side of the centrum 

 to the anterior and inferior surface of the transverse process midway between the extremity 

 of that process and its point of union with the neural arch. The anterior and median dorsal 

 ribs are stout and much arched, while the posterior are more slender and straighter. 



THE CAUDAL RIBS. 



These are reduced to short, straight, pointed ossicles at the extremities of the transverse 

 processes, with which they early become coossified, though leaving a distinct trace of the suture, 

 as shown in fig. 57. The ribs soon disappear in the more posterior caudals. The caudal ribs 

 differ from the presacral ribs in being single headed. 



THE FORE EIMB AjVD FOOT. 



All three of the elements of the fore limb are present in the Ceratopsia. The limb as a 

 whole is proportionally shorter than the hind limb and the individual bones are somewhat 

 more robust than are the corresponding bones of the hind legs. Thus the animal was not so 

 high at the shoulders as at the hips. This shortening of the fore limbs and feet in the Ceratopsia 

 is correlated with the abbreviated cervical region, which, as we have already seen, consists of 

 seven [eight] short vertebrae. These conditions enabled the animal readily to bring the anterior 

 extremity of the head on a level with the feet, facilitated the necessary movements of the head 

 by reducing the range of possible motion, and gave increased power to the muscles controlling 

 those movements by bringing the fulcrum nearer the weight, conditions absolutely necessary 



