THE SKELETON OF THE NEWT. RIBS AND STERNUM. 145 



The branchial arches consist of a median piece, the 

 basi-branchial, which is ossified in the centre and cartila- 

 ginous at either end, and of two pairs of cerato-branchials 

 which are attached to the cartilaginous part (fig. 29, A, 8) 

 of the basi-branchial. The first cera to-branchial is chiefly 

 ossified, the second (fig. 29, A, 4) is a good deal smaller and 

 is cartilaginous. Both are united dorsally to a single epi- 

 branchial, which is terminated by a small cartilaginous area 

 at the free end but is elsewhere well ossified. 



C. THE RIBS. 



The ribs are short imperfectly ossified structures, bifid 

 at their proximal end where they articulate with the trans- 

 verse processes, and tipped both proximally and distally with 

 cartilage. The dorsal portion of the proximal end corresponds 

 to the tuberculum of the ribs of higher animals, and the 

 ventral portion to the capitiilum. Some of the anterior ribs 

 have a step-like notch on their dorsal surfaces. 



The second to twelfth ribs are fairly equal in size, but 

 further back they decrease slightly. The ribs which connect 

 the sacral vertebrae with the ilia are however large. The short 

 ribs borne on the anterior caudal vertebrae are cartilaginous. 



D. THE STERNUM. 



The sternum (fig. 22, A, 6) is a rather broad plate of 

 cartilage, drawn out posteriorly into a median process marked 

 by a prominent ridge. On its antero-lateral margins it bears 

 surfaces for articulation with the pectoral girdle. 



2. THE APPENDICULAR SKELETON. 



A. THE PECTORAL GIRDLE. 



This is of a very simple character, and remains throughout 

 life in an imperfectly ossified condition. It consists of a 

 dorsal scapular portion, and a ventral coracoid portion 

 partially divided into an anterior part, the precoracoid, and 

 a posterior part, the coracoid. 



R. 10 



