BLOOD-VASCULAR SYSTEM OF THE LORICATI 5 1 



also sends off several branches to the other abductor and ad- 

 ductor muscles, and shortly before the pelvic bones become 

 united posteriorly, the ventral artery makes a short dorsal bend 

 and bifurcates at right angles, one branch going to the basal 

 canal of the right ventral fin rays and the other to the left. 

 Each terminal branch of the ventral artery exhausts itself by 

 giving off a branch to the core of each ray ; proximally this 

 vessel runs in the center of the cavit}^ but soon divides, one 

 branch continuing caudad along the right side of the cavity, 

 the other the left. Usually from the left branch of the ventral 

 artery, but often from the right, a median vessel is given off 

 caudad, which passes along the ventro-median line between the 

 2 great lateral muscles and exhausts itself in numerous inter- 

 costal arteries. 



This series of complicated vessels arising from the ventral 

 ends of the efferent branchial arteries and anastomosing with a 

 trunk of the subclavian artery may be comparable to the ves- 

 sels described by Miiller (pp. 36 and 37) as epigastrische Arte- 

 rien, and the ventral arter}- or ramus epigastricus decendens of 

 Miiller may be analogous to the mammaria interna of mammals. 



3. Carotid Arte^'ics. 



The short common carotid arteries (PL I, figs, i and 5 ; 

 C.Car.A.) arise from the* dorsal-cephalic corner of the first 

 efferent branchial arteries, and passing cephalad a short dis- 

 tance, about I cm., divide into the large external and internal 

 trunks. 



{ci). External Carotid or Carotis Posterior Artery (Pis. I 

 and II, figs. I, 5 and 15; E.Car.A.). — This vessel at once 

 makes a dorsal-cephalic curve, passing through a foramen 

 formed by a lateral process of the prootic, in company with, but 

 directly below the jugular vein. Leaving this canal with the 

 infraorbitalis or truncus buccalis-maxillo mandibularis and 

 just ventrad and caudad of the external jugular vein, the exter- 

 nal carotid passes over the dorsal edge of the hyomandibular, 

 along the posterior border of the orbit, and then runs ventro- 

 caudad beneath the levator muscle of the palatine arch and the 

 adductor mandibular muscles. It passes along the inner side of 



