BLOOD-VASCULAR SYSTEM, ETC., OF AMIURUS CATUS. 425 
The subclavian arteries are the largest and most anterior pair of the 
intercostales. They arise from the dorsal surface of the aorta descendens 
in the groove upon the fourth vertebra, and issue by foramina be- 
tween it and the third. They pass outwards along the anterior surface 
of the transverse processes of the fourth vertebra beneath the strong 
peritoneal continuation of the aponeurotic membrane. Hach artery 
gives off two branches to the muscles of this region and then turns for- 
wards, over the head-kidney and downwards to the median spine of 
the scapula, at which point it distributes itself. Three or four 
branches to the anterior portion of the ventral musculature of 
the trunk ; a branch to the pectoral fin and its muscles, which also 
sends a strong branch backwards on the outer surface of the muscles 
of the wall, and a branch which passes forwards beneath the girdle 
and anastomoses with certain of the hyoidean arteries are supplied 
by it. 
The arteries of the head have already been mentioned. It remains 
to add a short description of their relations and distribution. 
A few small twigs arise at the junction of the branchial veins for 
the aponeurotic wall and the fatty tissue on the base of the skull. 
An artery from the united first and second branchial veins, which 
I shall designate as pharyngo-branchial, passes down around the 
pharynx, which it supplies with blood, and also gives branches to the 
posterior /ev. branchiales, and in some cases the pharyngo-branchiales. 
Small arteries for the anterior Jev. branchiales arise from the first 
branchial vein near the origin of the carotids. 
The A. carotis externa arises from the dorsal surface of the first 
branchial vein at the angle where it turns backwards to join the 
second. (Pl. VIII. Fig. 1, c.ex). There is neither carotis commu- 
nis nor circulus cephalicus in Amiwrus. It passes upwards over the 
lateral surface of the JV. trigeminus on to its dorsal surface and along 
the ramus mandibularis towards the eye. A large branch supplies the 
abductor mandibule turning backwards beneath the muscle and also 
sending a branch through the mesethomoid bone to the nasal sac. 
A second branch passes beneath and behind the eye, also terminating 
at the nasal cavity. After giving a branch to the antero-lateral 
portion of the roof of the mouth, the remainder of the artery turns 
outwards, beneath and slightly anterior to the eye, and divides into a 
branch to the large maxillary barblet and another to the mandible. 
