VERTEBEATA. 



103 



fied, but a good example may be obtained in the human 

 thorax, or in the caudal vertebra of a bony fish. 



As a general rule, the vertebral column is divisible into a 

 number of distinct regions, of which the following are recog- 

 nisable in man and in the higher Vertebrata: 1. A series 

 of vertebrae which compose the neck, and constitute the 

 "cervical region" of the spine (fig. 481, c). 2. A number 

 of vertebrae which usually carry well -developed ribs, and 

 form the "dorsal region" {d). 3. A series of vertebrae 

 which form the region of the loins, or " lumbar region " (h). 

 4 A greater or less number of vertebrae which constitute the 

 " sacral region," and are usually amalgamated or " anchy- 



Fig. 481. — Skeleton of an Armadillo, showing the regions of the vertebral column, c, Cervi- 

 cal region ; d. Dorsal region ; I, Lumbar region ; s, Sacral region ; t, Caudal region or tail. 



losed " together to form a single bone, the " sacrum " (.s). 

 5. The spinal column is completed by a variable number 

 of vertebrae which constitute the " caudal " region or tail {t). 

 As regards the skull of the Vertebrates, the most import- 

 ant points to be noticed are the manner in which the 

 cranium articulates with the vertebral column, and the 

 structure of the lower jaw or " mandible." In Birds and 

 Eeptiles the skull articulates with the first vertebra of the 

 neck by means of a single articulating surface or " con- 

 dyle," carried upon the occipital bone. In the Amphi- 

 bians, again, and in the Mammals, there are tivo "occipital 

 condyles," by which the skull is jointed to the neck. The 

 lower jaw is sometimes wanting, but, when present, it con- 

 sists in all Vertebrata of two halves or " rami," which are 



