46 ALLEN 
and third efferent branchial arteries on one side anastomose 
with the corresponding trunks of the opposite side. From 
either side of the ventral point of union of the first pair of effer- 
ent vessels, a large hyordean artery (figs. 1 and 12, Hyo.A.) is 
given off to the hyoid arch and mandibular region. The ven- 
tral points of union of the second and third pairs of efferent 
branchial arteries mark the source of the ventral artery (Pls. 
I and II, figs. 1 and 12; Ven.A.); and the pharynx artery (Pl. 
II, fig. 12; Phar.A.) may arise form either of the third efferent 
branchial arteries. From the dorso-cephalic surface of the first 
pair of efferent branchial vessels, the 2 common carotid arter- 
tes (Pl. I, figs. 1 and 5; C.Car.A.) are given off cephalad; con- 
tinuing dorso-caudad, the first efferent trunk unites with the 
second to form the frst or antertor epibranchial artery (Pl. I, 
fig. 5; Epbr.A.(,)), and in like manner the third and fourth 
efferent branchial vessels unite to form the second or posterior 
epibranchial artery (Pl. I, fig. 5; Epbr.A..). The epibranch- 
ial vessels on one side unite with the corresponding trunks on 
the opposite side, forming a common chamber (Pl. I, fig. 5; 
C.C.), which lies in a median line ventrad of the basi-occipital. 
This chamber is the source of several large trunks; the dorsal 
aorta (Pl. I, figs. 1 and 5; D.Ao.) arising from the left posterior 
dorsal corner; the ca@léaco-mesenteric (Pl. I, figs. 1 and 5; Cee. 
Mes.A.) below and to the right; and the common subclavian 
trunk (Pl. I, fig 5) lies above the aorta and the cceliaco-mesen- 
teric artery. In one case the subclavians were seen to arise 
separately. The left one had its origin in the same place as 
the common subclavian trunk, and the right one came from the 
cceliaco-mesenteric artery. 
2. Arteries Arising From the Ventral Ends of the Efferent 
Branchial Arteries. 
First under this head might be mentioned the 2 little Ayo hyozd- 
eus tnfertor arteries (Pl. II, fig. 12; Hys.A.), which arise from 
the cephalic surface of the first efferent branchial arteries just 
before they unite ventrally. These vessels run cephalad a short 
distance and then spread out laterad over the dorsal surface of 
their respective muscles. 
