24 



PLEISTOCENE MAMMALIA. 



from that of the rhinoceros. The ankyloses! caudal (pseudo-sacral vertebrae) have 

 short rounded neural spines and broad wing-like transverse processes which unite 

 one with another distally. There are about fourteen free caudal vertebrae, the 

 anterior of which have low neural spines like those of the sacrals, and rather 

 long-, narrow flattened transverse processes. 



d. The Ribs and Sternum. 



The ribs, of which there are fifteen pairs, have the broad flattened form so 

 characteristic of Ungulates. Almost the whole trunk is embraced by them. Six 

 pairs meet the sternum, being connected with it by imperfectly ossified sternal 

 ribs, which rapidly increase in length as the series is followed back. 



Fig. 8. — Eight scapula seen from the outer side. \ natural size. Prom Harrington and preserved in 

 the Sedgwick Museum, Cambridge, a, glenoid cavity ; ''.spine: c, coracoid process ; &, coracoid border ; 



e, glenoid border. 



There is a large compressed and keeled presternum bearing a pair of juxta- 

 posed facets for articulation with the first pair of ribs. The mesosternum consists 

 of four segments, the first being laterally compressed, the last two dorso-ventrally. 

 The second is laterally compressed in front, but wide behind. The ossified part of 

 the xiphisternum is narrow and pointed, but it terminates in a broad cartilaginous 

 plate. 



e. The Shoulder Girdle. (Text-figure 8.) 



The scapula (Text-fig. 8) has a strong spine, but the acromion is not 



prominent. The coracoid process is well marked and slightly hooked and 

 upturned. 



