712 
PROFESSOR T. J. PARKER ON THE 
{anterior facial vein , Ant. fac. V.) is apparently discharged into it; hut I have never 
been able to get a satisfactory injection of this vessel. 
The only reference to the orbital sinus I have met with is the following somewhat 
obscure statement given by Milne Edwards (14) on the authority of Robin, whose 
paper* I have unfortunately been unable to consult. “ Les veines jugulaires coin- 
muniquent entre elles par un tronc anastomotique assez large, et constituent en 
general, derriere les orbites, un sinus plus ou moins vaste. II est extreme- 
ment developpe cbez les Squales, et constitue de chaque cote des branchies un 
vaste reservoir qui s’etend dans les cavites orbitaires.” This paragraph would seem to 
intimate that, the anterior ends of the jugular veins communicate directly with one 
another, which they certainly do not in Mustelus; indeed, from their position, any 
such union is anatomically impossible. 
The anterior cerebral vein. 
This (Plate 35, tig. 8, Ant. cereb. V.) is a paired vein receiving the blood from the 
olfactory lobe, and from its own side of the prosencephalon, diencephalon, and mesen¬ 
cephalon. At the level of the diencephalon it turns directly outwards, passes through 
a foramen in the side wall of the skull, and discharges itself into the orbital sinus. 
The blood from the rest of the brain is returned by the posterior cerebral veins 
which will be considered later (p. 715). 
The hyoidean sinus. 
This (Plate 34, tig. 2 ; Plate 35, fig. 10, Hyoid, S.) is a wide irregular vessel lying- 
on the outer face of the hyoid arch, parallel to the first afferent branchial artery 
(Af. hr. A. 1). In the middle part of its course it is double, consisting of two 
parallel trunks which unite with one another above at about the level of the junction 
of the epi- and cerato-hyal, below at that of the junction of the cerato- and hypo-hyal. 
The hyoidean sinus discharges into the interior end of the jugular vein by an 
aperture on its ventral wall, guarded by a single valve. Ventrally it is continued 
forwards to the symphysis mandibulse, parallel to and mesiad of the sub-mental artery, 
this portion of the sinus being the equivalent of a sub-mental vein. 
The right and left hyoidean sinuses communicate with one another by two wide 
anastomotic trunks (fig. 2, u), one immediately cephalad, the other immediately 
caudad, and both of them ventrad of the common stem of the first and second 
afferent branchial arteries. Close to the junction of the hindermost of these anasto¬ 
motic trunks the inferior jugular vein {Inf. jug. V .) communicates with the hyoidean 
sinus. 
* Robin, “ Sur le systeme veineux des poissons cartilagineux,” ‘ Compt. Rend.,’ vol. 21, 1845, 
p. 1282. 
