440 



C. H. DANFORTH 



m. adh. 



oper. 



OS. den. 



OS. mx. 



Fig. 16 Sketch of the external carotid and its branches. The deeper parts 

 are indicated by lighter lines. 



branch crosses the posterior face of the antorbital cartilage and 

 then goes through a foramen into the nasal capsule. How far 

 this perforating branch is homologous with the anterior end 

 of the orbitonasal artery which perforates the antorbital process 

 of teleosts it is difficult to say. 



The artery of the rostrum (fig. 17), the terminal extremity 

 of the external carotid, enters the snout by passing across a 

 broad groove beneath the antorbital process. It then bends 

 dorsally and, lying under the overhanging dorsal expansion of 

 the central cartilaginous core, retains its individuality nearly 

 to the anterior end. In its course through the rostrum it gives 

 off a series of long medial vessels, which lie close to the carti- 

 lage except near their terminations where they may turn laterad, 

 and another series of short lateral vessels, some of which actually 

 arise on the medial side and then pass around the main stem 

 dorsally. Through the greater part of its length the rostral 

 cartilage is hollow and filled with fat behind and a kind of mucous 

 tissue in front. The nutrient artery to this tissue arises from 

 the main vessel shortly after the latter enters the rostrum. At 

 its origin it bends somewhat caudad and then goes through a 



