BLOOD-VASCULAR SYSTEM OF THE LORICATI 85 
the auditory vein anastomoses with the cerebellum vein (Pl. III, 
figs. 23 and 25; Cer.V.), which arises in and leaves the cere- 
bellum with the cerebellum artery, but below it. In its ventral 
course it receives a superficial branch from the posterior surface 
of the optic lobe, and, after uniting with the auditory vein, the 
combined trunk continues cephalad a short distance between 
the optic lobe and the hypoaria and ventrad of the posterior 
cerebral artery before receiving the mesencephalic vein (See 
fig. 23). The mesencephalic vein (Pl. III, figs. 23 to 25; Me. 
V.) arises from the floor of the mesencephalon (optic lobe) and 
penetrating ventrad through the crus, passes out between the 
optic lobe and the hypoaria, in front of the III nerve and 
mesencephalic artery, then crossing below the nerve and artery 
it unites with the common vessel formed by the anastomoses of 
the auditory and cerebellum veins to form the fosterzor cerebral 
vein (figs. 23 to 25; P.Cer.V.). The course of this vein is 
cephalad, directly below the posterior cerebral artery, between 
the optic lobe and hypoaria, and between the trigemino-facial 
complex and the IV nerve. Uniting with the anterior cerebral 
vein midway between the cerebrum and the optic lobe it forms 
the encephalic vein (Pls. I, II and III, figs. 1, 15, 23 and 25; 
Enc.V.), which shortly leaves the IV nerve to follow trigemino- 
facial complex, and when the facialis portion of the ramus 
lateralis accessorius is given off the cranzal cavity vetn is re- 
ceived. This vein (Pl. III, fig. 24; C.C.V.) follows along the 
anterior surface of this nerve and anastomoses caudad with a 
branch of the posterior encephalic vein, which follows along 
the posterior surface of the vagus portion of the ramus lateralis 
accessorius. Hence the venous blood from the adipose tissue 
of the cranial cavity may reach the jugular vein through the 
encephalic, or the posterior encephalic vein, or through both. 
Then leaving the trigemino-facial complex, along the inner 
surface of the ciliary nerve, the encephalic vein penetrates with 
it through the most anterior foramen in the prootic, and here 
empties into the internal jugular just before it unites with the 
orbitonasal and external jugular in forming the main jugular 
vein. 
(c) Orbito-nasal Veins (Pls. I, II and III; figs. 1, 5, 13, 15, 
