BLOOD-VASCULAR SYSTEM OF THE LORICATI 6l 



of the nasal sac. They penetrate the base of the filaments 

 with branches of the olfactory nerve, and running through the 

 inner connective tissue layer send off branches into the secon- 

 dary or branching filaments. The main orbito-nasal trunk 

 after passing behind the nasal sac with the corresponding vein 

 and the olfactory nerve divides into a cephalic and a ventral 

 branch. The smaller cephalic branch, crossing behind the or- 

 bito-nasal vein, proceeds above it, and becomes the maxilla 

 artery (Pis. I and III, figs, i, 17 and 18; Max.A.(,)). This 

 artery in turn also breaks up into 2 vessels ; a dorsal one, which 

 penetrates the premaxilla ; and a ventral one, which runs along 

 the posterior surface of the premaxilla. The larger ventral 

 branch is ihQ posterior maxilla artery (Pis. I and III, figs, i, 17 

 and 18 ; Max. A.(2)) ; at the ventral edge of the nasal sac it sends 

 a branch inward to the palatine arch ; and directly below this 

 branch at least 2 ventral nasal sac arteries (PI. Ill, fig. 17;. 

 N.S.A.(.)) are given off dorsad, which supply the ventral fila- 

 ments in a like manner to dorsal nasal sac arteries. Then an- 

 astomosing with the much smaller facialis-maxillaris artery it 

 runs along and breaks up on the outer surface of the adductor 

 mandibul^e muscle, immediately behind the maxilla. 



(c) Summary of the Carotids. — Parker has well said (60, P. 

 653), that : " The application of the name ' carotid ' to the ce- 

 phalic arteries of fishes must of course be taken to imply nothing 

 more than a general correspondence with the similarly named 

 vessels in the higher Vertebrata." For example, his anterior 

 carotid (internal carotid) in Mustelus (60, fig. 6), and the similar 

 artery in Hydrolagtis, Chimajra(Pl. Ill, fig. 26; I. Car. A.), are 

 almost analogous to the ophthalmic artery of Ophiodon (PI. I, 

 figs. I and 5 ; Oph. A) provided that it anastomosed with the orbito- 

 nasal artery with which it comes in such close contact. In the 

 same connection, Parker proposes to substitute the names ante- 

 rior and posterior carotids for the internal and external carot- 

 ids. This substitution may seem advisable in the Selachians, 

 where the carotids at first occupy a distinctly anterior and pos- 

 terior position ; but in the case of the Teleosts that I have exam- 

 ined the vessel which has been designated as the internal car- 

 otid has a distinctly profundus course, and the external carotid 



