438 C. H. DANFORTH 



Neither of the above arteries seems to fill completely the 

 place of the external carotid of Amia although the second comes 

 very near to it and, with the first, also covers the hyoopercular 

 of that form. The teleostean vessel which Silvester, endeavor- 

 ing to follow Allis, called the hyoopercular artery, but which, 

 as Allis subsequently ('08 c) pointed out, is presumably com- 

 parable to the external carotid of Amia, finds a more or less 

 complete homologue in the two vessels above described. The 

 fact that they arise separately from a longitudinal trunk and 

 not by a single stem from one of the several points where the 

 'hyoopercular' ('external carotid') may appear in other forms, 

 is probably of little morphological import. The branch (a. com.) 

 from the anterior of these, which is described above as crossing 

 beneath the epithelium of the spiracular cleft, was not found 

 to connect directly with the spiracular vessel although it is 

 strongly suggestive of the commissure that occurs here in Amia, 

 the Loricati, and the teleosts described by Silvester. 



The further continuation of the external carotid, apart from 

 its proximal connection, is very much like the artery in teleosts 

 which Silvester calls the external carotid and Allis ('08 c) the 

 orbito-nasal. It is partly encircled by the a. opthalmica magna 

 (fig. 15, a.om.) just as is the orbitonasal (Allis) in teleosts and, 

 like that artery, it forms a large longitudinal trunk suppljdng 

 branches to the orbit, eye muscles and nasal region. After 

 leaving the facial canal and giving off its second bran' h as above 

 described, it runs forward medial to the anterior portion of the 

 protractor hyomandibularis already referred to. Along this 

 part of the course there arise several small twigs probably of 

 no morphological importance. As it approaches the mandibu- 

 lar nerve it turns somewhat laterad under the protractor man- 

 dibularis muscle where it gives off the large facial artery and 

 then continues forward beneath the orbit and recti muscles. 

 Allis (1. c, p. 285) describes the external carotid as terminating 

 here by dividing into the 'orbito-nasal and maxillo-mandibularis 

 arteries.' 



The facial artery (figs. 15, 16, a.fa.) passes over the nerve to 

 its anterior side and then follows it out, lying at first on the 



