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accompanied by the orbito-nasal vein, passes through a perforation of 

 the side wall of the skull, and entering the cranial cavity near the 

 base of the nervus olfactorius, accompanies that nerve in its forward 

 course into the nasal sac. The further peripheral distribution of the 

 artery was not traced. 



The external carotid artery, after giving off the branch that 

 accompanies the ramus palatinus posterior facialis, runs upward and 

 forward along the outer surface of the skull and breaks up into several 

 branches which accompany the several branches of the trigemino-facialis 

 complex; but the distribution of this artery was not traced farther 

 than was necessary to establish that there was no special branch des- 

 tined to the eye ball. That some small branch or branches of this 

 artery may be sent to the eye ball, such as Allen describes in the 

 Loricati, is possible, but they were not found. The artery does not 

 apparently traverse a trigemino-facialis chamber, for although it would 

 seem as if this chamber must be present in some form, there is no 

 proper indication of but one cranial wall in this region, and that one 

 wall would seem to be the inner wall of the chamber; for both the 

 external carotid and the jugular vein He external to it. Whether the 

 nervus sympatheticus is also extracranial in the trigemino-facialis 

 portion of its course, or not, I can not determine, for I could not trace 

 the nerve in my sections. Herrick ('01) says that the "sympathetic 

 chain enters the trigemino - facial ganglionic complex with the hyo- 

 mandibular trunk", and as he says that the "whole of the trigemino- 

 facial complex is intra- cranial", it would seem as if the sympatheticus 

 must here enter the cranial cavity. 



The arteries of Ameiurus, as above described, are shown in the 

 accompanying purely diagrammatic figure, which is constructed on ex- 

 actly the same principles as the figures illustrating my two other works 

 on this same subject (Allis, 2 and 3). A comparison of the several 

 diagrams shows that the afferent prebranchial arteries of Ameiurus 

 resemble those of Amia, while the efferent and carotid arteries, except 

 in the absence of a hyoidean artery and gill, resemble quite closely 

 those of Polypterus. This suggests, at once, that the so-called pseudo- 

 branch of Ameiurus may be a structure related to the thymus of Poly- 

 pterus (Pollard, '92), a subject that will be again referred to after 

 some consideration of the cephalic trunk of the internal carotid artery 

 in Teleosts. 



In existing descriptions of the Acanthopterygii the typical arrange- 

 ment of the carotid arteries would seem to be that the internal carotid 

 artery, after separating from the external carotid, runs forward along the 



17* 



