BLOOD-VASCULAE SYSTEM OF THE TILE-FISH. 105 



craniad, giving off a small branch to the cranial portion of the kidney, several 

 branches to the muscles on the dorsal and caudal surface of the skull in the region 

 of the supraoccipital bone, and finally, branches which terminate in the skin and 

 cephalic crest, (b) A branch (79) which supplies the thymus eland" and adjacent 

 muscles, (c) In addition to several small muscular branches, the coracoid artery (80) 

 of Parker & Davis (1899) a short distance from the base of the pectoral fin. this 

 vessel extending- ventrad, close to the pericardium, and giving off numerous small 

 muscular branches. At a point opposite the cranial end of the basipterygium, either 

 the right or left coracoid artery joins the median hypobranchial. (d) The brachial 

 artery (81) which supplies the pectoral tin. (e) The ramus epigastricus descendens (82), 

 which runs caudad close to the skin and supplies the ventral abdominal muscles as 

 far as the cloaca. 



The parietal mi* /■!<■•< and thevr tranches (tig. 1«'>. pi. i. tig. 15). The parietal 

 arteries (83) arise from the dorsal aorta along its entire length, a pair opposite every 

 other vertebra. They will lie described in order. 



The first pair are given off, as a rule, opposite the third vertebra, and. one on 

 each side, curve laterad, dorsad, and craniad. then, after sending small branches 

 to the cranial portion of the kidney, run dorsad to supply the dorsal parietal 

 muscles. 



The second pair are given off opposite the fourth vertebra, and run laterad 

 through the kidney, to which both send one or more small arteries (Sj t ). At a point 

 just lateral to the kidney each of the pair divides into a peritoneal, an intermuscular, 

 anil a dorsal branch. The peritoneal branch (85) runs ventrad close to the peri- 

 toneum and supplies the lateral abdominal muscles of that region. The intermuscular 

 branch (67) extends laterad along the intermuscular bone to supply the adjacent 

 muscles. The dorsal branch of the left side (88s) is small and runs dorsad to the 

 membranes and muscles adjoining the fourth vertebra; the corresponding artery of 

 the right side (88d) is quite large and runs dorsad, between the neural spines of the 

 fourth and fifth vertebra', to the lower end of the pterygiophores of the dorsal tin, 

 where it divides into several muscular branches, two of which run dorsad, one on 

 the right (89d) and one on the left (89a), Close to the skin each of these two branches 

 divides into an anterior and a posterior vessel, the anterior running craniad and sup- 

 plying the skin, while the posterior runs caudad to anastomose with the correspond- 

 ing anterior branch of the next dorsal artery. The pairs of dorsal branches are 

 throughout bilaterally asymmetrical, the larger branches being sometimes on one 

 side and sometimes on the other. The smaller branch of each pair supplies the 

 structures adjacent to the vertebral column. The larger branch, as already described, 

 sends off on each side of the base of the dorsal fin an anterior and a posterior vessel 

 which anastomose, respectively, with the posterior and anterior corresponding 

 adjacent arteries, thus forming a more or less continuous vessel (90) on each side of 

 the base of the dorsal tin. These vessels send numerous small branches (91) to the 

 skin and dorsal fin. 



u The thymus gland of the tile-fish is situated in the dorsal part of the gill chamber jusf cranial to the supra-clavicle. 

 [n fishes of about 50 em. in length it is a triangular gland about 17 mm. long and 9 mm. wide; in tin- large individuals— those 

 of about S5 em.— it is very much reduced in size, traces of it. how ever, being alw ays present. 



