BLOOD-VASCULAR SYSTEM OF THE LORICATI 53 



ciliary nerve and internal jugular vein it passes cephalad out 

 of the skull through the large olfactory-optic foramen, then 

 curving laterad in company with the ramus ciliaris longus and 

 the iris vein it crosses under the orbito-nasal vein and the trun- 

 cus supra-orbitalis, passing between the superior and external 

 rectus muscles, gives off a branch to the latter (PI. II, figs. 13 

 and 15 ; Ex.R.A.). Then running laterad across the posterior 

 dorsal surface of the eyeball it penetrates the sclerotic coat in 

 its median line, and continuing laterad in the silver layer of the 

 choroid until the iris is reached, where, with the ramus ciliaris 

 longus, it bifurcates into 2 ventral vessels, which supply at 

 least the dorsal half of the iris. The normal arrangement of 

 the iris vessels is first the iris vein, then the ramus ciliaris lon- 

 gus, and finally the iris arter}'-, but in several cases I have 

 observed the artery curving cephalad and passing between the 

 nerve and the vein. 



The second vessel is given off a little below the sclerotic-iris 

 artery ; and after making a rather sharp caudal curve terminates 

 in the levator arcus palatini muscle. The next vessel is the 

 facialis-maxillaris artery (PL I, fig. i ; F.Max. A.) which arises 

 cephalad from the external carotid in the region of the orbit, 

 and passes obliquely over the external jugular vein and the ramus 

 mandibularis or the ramus maxillaris inferior, where it gives off 

 a large ventral branch, \.hQ facial artery (PI. I, fig. i ; F.A.), 

 for the adductor mandibul^e muscles. This branch runs along 

 the lateral surface of the deeper portion of the adductor mandi- 

 bulas, giving off numerous branches to the adductor muscles, 

 but does not follow the nerve to the mandible. The main por- 

 tion of the facialis-maxillaris artery proceeds along the floor of 

 the orbit in the adductor arcus palatini muscle, to which it gives 

 off numerous branches, and when the level of the nasal sac is 

 reached it receives a much larger artery from the orbito-nasal 

 artery (Pis. I and III, figs, i and 17 ; O.N. A.), which is a 

 branch of the internal carotid artery.^ This combined vessel 

 continues in a cephalic direction, supplying the region directly 



1 McKenzie (52, p. 427) mentions the crossing of the branches of the ex- 

 ternal and internal carotids in the neighborhood of the nasal sac, in Avieiurtis 

 but nowhere have I met with the statement of their union. 



