278 



MAMMALIA. 



other class of Vertebrates ; but it presents great variations in this 

 respect in the individual groups, more especially with regard to the 

 development of the face, the prominence of which in general varies 

 inversely with the development of the intellectual faculties (Camper's 

 facial angle). The hyoid bone is reduced to a transverse, bridge-like 

 piece (body of the hyoid), with two pairs of cornua. In Mycetes it 

 is largely developed and excavated. 



The vertebral column, except in the Cetacea, is divided into five 

 regions, viz., cervical, thoracic, lumbar, sacral and caudal (fig. 669). 

 In the aquatic Cetacea, which are without hind limbs, the lumbar 



H 



FIG 669. Skeleton of the Lion (after Giebel; Bronn's Classen und Crdnungen). St, sternum; 

 Sc, scapula ; J3T, humerus ; -B, radius ; U, ulna ; Cp, carpus ; Me, metacarpus ; Jl, ilium 

 P, pubis; Js, ischium; Fe, femur; T, tibia; F. fibula; P, patella; Tg, tarsus; Mt, 

 metatarsus ; C, calcaneum. 



region passes gradually into the caudal; on the other hand the 

 cervical region is strikingly shortened, and the fusion of its anterior 

 vertebrae renders it rigid and immovable. The vertebral bodies are 

 only exceptionally (neck of Ungulates) connected by articular sur- 

 faces, but are usually joined by elastic discs (intervertebral ligaments). 

 The first cervical vertebra (atlas) is a bony ring with broad, wing-like, 

 transverse processes, on the articular surfaces of which the two 

 occipital condyles rest and permit of the head being raised and 

 depressed. The turning of the head to the right and left is effected 

 by the movement of the atlas about a median process the odontoid 

 process of the next vertebra, which is called the axis (epistropheua). 



