488 



apparently forming a long and continuous vessel, the posterior 

 carotid of current descriptions, which artery gives off the external 

 carotid, this latter artery giving off or receiving the lateral dorsal 

 aorta. And it furthermore seems certain that the flow of blood must 

 be from the efferent hyoidean artery into the external carotid, the 

 current running posteriorly through that short section of the 

 lateral dorsal aorta that lies between the efferent hyoidean and ex- 

 ternal carotid arteries. A strictly similar origin of the external 

 carotid is shown in Hyrtl's (1872) figure of Scyllium canicula, while 

 in Acanthias vulgaris (Hyrtl), Mustelus antarcticus (Parker) and 

 Chlamydoselachus (Allis) the external carotid has its origin from the 

 lateral dorsal aorta considerably anterior to the point where that 

 artery is joined by the efferent hyoidean artery. 



The external carotid, after its origin from the lateral dorsal aorta, 

 runs at first forward and laterally and soon gives off two dehcate 

 branches arising close together but from opposite sides of the artery. 

 One of these branches runs antero-mesially and enters the foramen 

 by which the facialis nerve issues from the skull, while the other runs 

 ventro-postero-laterally, accompanying the facialis nerve, and appa- 

 rently goes to muscles and tissues of the region; these branches re- 

 calling the little arteries that are sent to the glossopharyngeus and 

 vagus nerves and that have been above described. The external 

 carotid then breaks up into three parts, an ophthalmicus branch 

 which accompanies the ophthalmicus nerves and supplies the muscles 

 of the eye, a maxillaris branch which goes to the region of the upper 

 jaw, and a mandibularis branch which goes to the mandible. 



The lateral dorsal aorta, after giving off the external carotid, 

 becomes the homologue of the internal carotid of current descriptions 

 of ganoids and teleosts, and having received the efferent hyoidean 

 artery, turns sharply dorso-antero-mesially, almost at a right angle, 

 in the direction prolonged of the efferent hyoidean artery, and enters 

 the carotid canal of Gegenbaur's (1872) descriptions of the chon- 

 drocranium. Eunning mesially and upward in that canal it meets and 

 fuses with its fellow of the opposite side to form a single, much en- 

 larged median vessel. This vessel turns upward in a median canal 

 in the cartilage which is undoubtedly the one shown in Gegenbaur's 

 Pig. 1, Taf. IV, but in my specimen the ventral portion of this canal 

 is much larger and more important than Gegenbaur's figure would 

 seem to indicate. The median vessel is a broad, firm, flat and somewhat 



