98 



BULLETIN OF THE BUREAU OF FISHERIES. 



and, in common with the latter, supplies the pseudobranch as described above. In 

 the two cases where the direct afferent pseudobranchial artery was found to be present, 

 this latter branch was small and did not join the hyoidean artery. 



The second division of the a. hyoopercularis {21), running- caudad and ventrad 

 just medial to the upper end of the hyomandibular. sends a small branch to the m. 

 adductor hvomandibularis. and supplies* the mm. adductor and levator operculi. 



The remaining or third branch of the a. hyoopercularis {22) divides into a supra- 

 orbital and a postorbital branch. 

 The supraorbital branch {23) runs 

 craniad on the dorsal wall of the 

 orbit; the postorbital branch (.'/) 

 supplies the m. levator arcus pala- 

 tini and membranes behind the 

 orbit. According to Allis (1901) 

 the a. hyoopercularis in Amia 

 represents the dorsal portion of 

 the hyoidean aortic arch. 



In the teleosts this vessel may 

 arise in three different ways: From 

 the first efferent branchial artery, 

 as in Microgadus (fig. !»): from the 

 junction of the first efferent bran- 

 chial artery with the carotid, as in 

 Opsanus and Spheroides (tigs, lo 

 and- 7); and from the common 

 carotid, as in the tile-fish. 



After giving off the a. hyo- 

 opercularis. the carotid continues 

 craniad for a short distance, 

 pierces the skull wall between the 

 parasphenoid and profitic, and 

 immediately divides into the 

 internal and external carotid 

 arteries. 



Tin external carotid artery 



Fig. 10. — Cranial portion of the arterial system ia the toad-fish ( Opsanus 7 V 7 7 id 1 £ l \ 



fa«). Ventral view, natural size. On the right side the ventral ends '""' ,fs OTanC/ieS (tig'. 1<>. pi. 1). 



of the efferent branchial arteries and their branches are reflected so (^\ Two small branches are c'ivetl 



as to bring thein into one plane, j. .. ,, , ,.j 



on from the external carotid near 



its origin. The larger {30) runs laterad and divides into two branches which supply 

 the external and superior recti muscles of the eye. The artery that supplies the 

 hitter muscle runs along its inferior border and pierces the sclerotic to enter the eye 

 (,7). The other branch is a small vessel ( ;.') which supplies the inferior and internal 

 recti muscles of the eye. These two arteries frequently arise by a single trunk from 

 the external carotid. 



(1>) Beyond the point of origin of the arteries supplying the recti muscles, the 

 external carotid artery lies close to the eyeball and in this position gives off two 



