BLOOD-VASCULAR SYSTEM OF TilE LORICATI 95 



did these 2 veins leave the pectoral fin canal in the same places ; 

 in fact, they were not the same in the 2 different fins of 

 the same fish. In the fin from which fig. 14 was drawn the 

 dorsal branch left between the seventh and eighth rays, count- 

 ing dorso-ventrad, and the ventral branch left in the neighbor- 

 hood of the fourteenth ra)'. Each of these branches proceeded 

 dorsad, for some little distance, along the inner surface of the 

 superficial pectoral adductor muscle, and each branch received 

 numerous smaller branches from the superficial and profundus 

 adductor muscles. Uniting on the level with the scapula fora- 

 men they form the internal subclavian trunk, which continues 

 dorsad behind the subclavian artery. Shortly before the kidney 

 is reached it curves caudad, and passing between the first few 

 spinal nerves and the superficial adductor muscle, pierces the 

 ventral surface of the corresponding fork of the kidney. Once 

 within the kidney the internal subclavian rapidly decreases in 

 caliber, by sending off branches that break up into capillaries, 

 which finally reach the cardinal through the renal veins. 



The vein desijinated as the external subclavian or subclavian 

 vein!^2) (PI- II> fig* 14 5 Sub.V.(.,)) has its origin from the super- 

 ficial and profundus pectoral abductor muscles, on the outer 

 surface of the pectoral arch. Coming through the scapula 

 foramen, cephalad of the external subclavian artery, it re- 

 ceives a branch from the profundus adductor muscle, and then 

 runs for a short distance below and behind the precaval vein, 

 where it receives the vein designated as the subclavian vein,^^) 

 (PI. II, fig. 14; Sub.V.(3)). This vein takes its source from 2 

 branches, one coming from the ventro-cephalic portion of the 

 profundus abductor muscle, and the other from the similar part 

 of the profundus adductor muscle. The former penetrates the 

 coracoid foramen, and unites with the latter in forming the main 

 subclavian vein,^), which passes dorsad along the inner surface 

 of the profundus adductor muscle. Leaving this muscle, 

 subclavian vein^g^ unites with the external subclavian vein to 

 form the subclavian sinus (PI. II, fig. 12 ; Sub.S.), which 

 empties into the sinus venosus directly behind the precaval vein, 

 but before uniting with the external subclavian, it receives a 

 vessel formed from a branch from the clavicle and the slcrno- 

 hyoideus vein (PI. II, figs. 12 and 14; Ster.V.). 



