374 
KAMAKICHI KISHINOUYE : 
branchial arteries, but a very small portion is sent ventralwards beneath the 
ventral aorta to form the hypobranchial artery, unappropriated named, which 
nourishes the heart, ventral fins, and the ventral carinales. In the Katsuwonidae 
tins artery is divided into paired branches behind the ventral fins. A slender 
artery runs backwards just above the ventral aorta to nourish the heart. The 
artery is formed by the union of branches of downward efferent branchial 
arteries in the third gill-arches. A part of the blood in the efferent branchial 
arteries is conveyed anteriorly by the carotid arteries to the cephalic region, 
but the greater part of the blood is earned backwards by the dorsal aorta. 
To the vertebral system arising from the dorsal aorta belong the renal 
arteries, subclavian, and in the case of the Plecostei, the cutaneous arteries. 
The subclavian arteries arise near the the root of the coeliaco-mesenteric artery 
in front of the pharyngeal muscles. They are short, and are soon divided 
into two branches, anterior and posterior. The posterior branch running 
obliquely backward becomes the subclavian or brachial artery for the pectoral 
fin. The artery is divided again into two or more, the exterior one of which 
goes to the extensor, the interior one to the retractor muscle of the pectoral 
fin. The segmental arteries are given off along the intermuscular bones, and 
also along neural and haemal spines. In the Scombridae and Cybiidae these 
segmental arteries are generally found in every other segment of the body. 
In the Plecostei, however, they are generally found in every segment. In 
the Cybiidae nearly all the precaudal hypaxial branches of the dorsal aorta 
give off short, dendritic renal arteries (fig. 6). In the Plecostei (figs. 4, 5) 
only horizontal segmental arteries are found in pairs in almost every segment 
of the body, and nourish the dark red portion of the lateral muscle, lying 
above the median horizontal network of the oblique tendons. Generally speak¬ 
ing the cutaneous arteries together with the median horizontal segmental arteries 
are the source of activity of plecostean fishes. In the Scombridae and Cybiidae 
these arteries are generally found in every other segment, but in the Plecostei 
they are found in every segment. 
The cutaneous arterial system consists of one or two large trunks running 
near the lateral median fine of the body, originating in the pectoral region, 
behind the pharyngeal muscle from the dorsal aorta. These arteries are 
nearly equally as large as the dorsal aorta itself. In Thunnus they originate in 
