I22 ALLEN 
unites with the hyoidean artery to form the mandibular artery, 
but in this genus the hyoidean artery branches in the region of 
the preopercle. The ventral fork passes through a foramen in 
front of the preopercle to become the mandibular artery; while 
the dorsal fork passes along the inner surface of the hyomandib- 
ular and anastomoses with the pseudobranchial artery. Usu- 
ally the pseudobranchial artery has its origin from the main 
stem of the external carotid (facialis-mandibularis) in the facial 
region, but with Axoplopoma the pseudobranchial artery rises 
from the external carotid close to its origin from the first effer- 
ent branchial artery; in fact it might be said to rise with the 
external carotid from the first efferent branchial artery, being 
fully as large as the carotid. An ophthalmic or efferent pseudo- 
branchial artery always rises from the efferent pseudobranchial 
arteries, which supplies only the choroid coat of the eye. In 
Ophiodon the ventral artery rises from the ventral union of the 
second and third pairs of efferent branchial arteries; while in 
the other genera it comes from the union of the second efferent 
vessels. This artery in Anoplopoma is a short vessel barely 
reaching the pelvic bones; the supply for the ventral fin region 
comes from the subclavian. In all the genera but Anoplopoma, 
the pharynx artery, from which the coronary rises, has its 
source directly from one of the second or third efferent bran- 
chial arteries, but in this genus it rises from the ventral artery. 
There is always a distinct circulus cephalicus formed by the 
union of the encephalic, internal carotid, common carotid, first 
efferent branchial, and the first epibranchial arteries. Both 
pairs of epibranchials terminate in a common chamber from 
which the dorsal aorta, cceliaco-mesenteric, and subclavians 
have their origin; in some cases, however, this chamber is 
simply an opening between the aorta and the cceliaco-mesen- 
teric. The dorsal aorta is essentially the same in all the gen- 
era; passing caudad beneath the vertebral column it gives off 
the renal and spermatic arteries to the kidney and the reproduc- 
tive organs, the neural, hemal, and intercostal arteries to the 
body wall, and finally terminates in the caudal fin. The sub- 
clavian arteries are practically the same in all the forms studied ; 
they may arise from a single trunk or separately as was de- 
