62 ALLEN 



a superficial one. Even though the cephalic portion of the 

 internal carotid crosses the tract of the external carotid and a 

 branch of one anastomoses with a branch of the other, still, in 

 the main, the internal carotid supplies the region of the internal 

 carotids of the Mammalia. It certainly extends no farther 

 cephalad than the exteral carotids. For these reasons, in 

 Op/u'odon, it seems advisable to retain the names internal and 

 external. 



4. Operaila?' and Do?-sal B?-anchial Muscle Arteries. 



These vessels are 2 ver}- constant arteries, which arise from 

 the dorsal part of the second efferent branchial arter3\ 



Of the 2, the opercular artery (PI. I, fig. i ; Op. A.) is the 

 most dorsal and cephalic vessel. It arises from the anterior 

 surface of the second efferent branchial artery near its point of 

 union with the first efferent branchial artery ; its course is first 

 cephalad for a short distance, passing over the second obliquus 

 dorsalis muscle, to which it gives a branch ; then curving dor- 

 sad, sends off a cephalic branch, which supplies the first inter- 

 nal branchial levator muscle (Levatores arcuum branchialium in- 

 tern! of Vetter) and the first obliquus dorsalis muscle ; and a little 

 farther up, a third arter}' is given off to the 4 outer branchial 

 levator muscles (Levatores arcuum branchialium externi of 

 Vetter). Then continuing dorsad, laterad to the first efferent 

 branchial artery and jugular vein, it sends off a caudal branch 

 to the levator operculi muscle of Vetter, and when the level of 

 the opercular is reached, terminates by running ventrad along 

 the inner surface of this bone. 



The vessel, which is designated as the dorsal branchial mus- 

 cle artery (PI. I, fig. i ; Br.M.A.), but which supplies fewer 

 branchial muscles than the one designated as the opercular 

 artery, arises from the posterior surface of the second efferent 

 branchial artery directly below the opercular artery. Its course 

 is caudad, passing behind the second internal branchial levator 

 muscle, and over the third and fourth obliqui dorsales muscles, 

 it sends off a branch to each. Then after crossing over the 

 fourth efferent branchial artery it curves ventrad, supplying the 

 occipito-clavicuhiris muscle, the pharynx, and the dorsal part of 

 the pharyngo-clavicularis internus muscle. 



