Another vessel arises from the middle of the anterior side of the first efferent branchial loop and runs forward to the spiracle, where it ends in the capillaries of the pseudobranch. This is the _afferent hyoidean artery_. The term pseudobranch is used for the branchial lamellae of the spiracle rather than demibranch because of the arterial blood supply of this organ. Immediately after uniting the internal carotids divide and diverge, forming an X-shaped figure. Each anterior limb of the X again divides into two branches. The lateral branch passes to the ventral surface of the skull; it presently gives off an anterior twig (_ophthalmic artery_) which enters the eye. It then passes on as the _efferent hyoidean artery_ to the pseudobranch. The inner of the two branchs mentioned above passes on as the _internal carotid, sensu strictu_, and is distributed to the brain. If the dissection is made with care, the branches of the internal carotid can all be found without cutting any important nerves. The branches passing to the eye and brain are best traced to their terminations in connection with the dissection of the nervous system. Near the union of the first pair of efferent branchial arteries a small _posterior vertebral artery_ arises from each, and runs anteriorly along the vertebral column. Near the divisions of the common carotids two _anterior vertebral arteries_ arise from these vessels and pass posteriorly, often anastomosing with the posterior vertebral arteries. These vertebral arteries are vestiges of the former anterior part of the dorsal aorta (compare with Eugaleus, in which the dorsal aorta sends forward two vessels which join the common carotids). An _oesophageal artery_ springs from the second efferent branchial, and passes back until it enters the wall of the oesophagus. It also gives off nutrient branches to the second, third, and fourth gill pouches. The nutrient artery of the first gill pouch arises directly from the first efferent branchial. Near the point at which the fourth pair of efferent branchials join the aorta, two small _subclavian arteries_ leave the aorta and pass into the pectoral fins. There is some variation in regard to the point of origin of these vessels; it may be either in front of or behind the junction of the fourth efferent branchials with the aorta.