ARTERIAL SYSTEM. 



251 



The principal branches of the dorsal aorta are the 

 following. 



i. The subclavian arteries are a pair of vessels, 

 which arise from the dorsal surface of the 

 aorta between the third and fourth pairs of 

 efferent branchial vessels, and run outwards 

 and backwards in the body-wall and along 



Fig. 52. — Soyllium canicula. Transverse eeetion passing through the 

 posterior dorsal fin. (a. m. m.) 



A, horny fibre. B, basal cartilage of the dorsal fin. C. mvotomes. D. ' 

 neural spine. E, base of neural arch. F, notochord. Gr calcified portion of 

 centrum. H h«mal arcb. I, spinal cord. K, lateral vein. L, caudal artery. 

 M, caudal rein. 



the hinder border of the pectoral girdle to 

 the pectoral fins, which they supply, 

 ii. The cosliac artery is a large median vessel 

 arising from the ventral surface of the aorta, 

 about half an inch behind the openings of the 

 last pair of efferent branchial vessels. It runs 

 backwards in the mesentery close to the dorsal 

 surface of the stomach, and divides into two 



