374 K.\MAKICHI KISHIXOUYE: 



braucLial arteries, but a very small j^wiiiou is sent venti'alwards beneath the 

 ventral aorta to form the hjjwbranchial aiierj-, imappropriiitely named, which 

 nourishes the heart, ventral fins, and the ventral carinales. In the Katsuwonidae 

 this artery is divided into paired branches behind the ventral fins. A slender 

 artery rans backwards just above the ventral aorta to nourish the heart. The 

 artery is formed by the miion of branches of downward efferent branchial 

 arteries in the third gill-ai'ches. A j^aii of the blood in the efferent branchial 

 arteries is conveyed anteriorly by the carotid arteries to the cephahc region, 

 but the greater part of the blood is canied backwtuds liy the dorsal aorta. 



To the vertebral system ai'ising fi-om the dorsal aorta belong the renal 

 ai-teries, subclavian, and in the case of the Plecostei, the cutaneous ai-teries. 

 The subclavian arteries arise near the the root of the coeliaeo-mesenteric artery 

 in front of the pharyngeal muscles. They are short, and are soon divided 

 into two branches, anterior and posterior. The posteiüor branch running 

 obliquely backward becomes the suljclaviau or brachial arteiy for the pectoral 

 fin. The aiieiy 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 bod^-. 

 In the Plecostei, however, they are generally foimd in every segment. Li 

 the Oybiidiie nearly all the precaudal hypaxial branches of the doi^sal aort^i 

 give off short, dendi-itic renal aiieries (fig. G). In the Plecostei (figs. 4, 5) 

 only horizontal segmental aiieries are found in paii-s in almost every segment 

 of the body, and nourish the dark red portion of the lateral muscle, lying 

 alx>ve the median horizontal network of the obHque tendons. Generally speak- 

 ing the cutaneous ai'teries together with the median horizontal segmental la-teries 

 are the source of activity of plecostean fishes. In the Scombridae jind Cybiidae 

 those ai-teries are generally found in every other segment, but in the Plecostei 

 they are found in every segment. 



The cutiuieous arterial STOtem consists of one or two lai-ge trunks r unning 

 near the lateral median line of the body, originatmg in the jx^türal region, 

 behind the phai-jugeal muscle horn the doi-sal aorta. These arteries are 

 nearly equsüly as lai'ge as the doi-sal aorta itself. In Tlmnnus they originate in 



