448 C. H. DANFORTH 



fin and in some cases at least, terminal branches around the 

 anus run forward on the rectum to become continuous or to 

 anastomose with the mesenteric artery. Posterior to the coelom 

 the vessels comparable to these partake more of the character 

 of the parietal arteries. About eight or nine pairs of them supply 

 the anal fin. 



The subclavian arteries (figs. 12, 15, a. sc.) have the general 

 relations of the other segmental arteries. They arise at a con- 

 siderable distance behind and entirely independent of the fourth 

 efferent branchial arteries. Each at once gives off the charac- 

 teristic dorsal branch which ramifies in the 'occipital region and 

 supplies the neural canal but was not found to anastomose 

 directly with the basilar artery, The lateral division runs ventrad 

 and laterad behind the jugular vein and in front of the post scapu- 

 lar. Aside from the anterior branches already described in con- 

 nection with the coronary and hypobranchial arteries, it gives 

 off posteriorly above the scapular a long superficial branch (a. thd.) 

 which is probably to be identified with the a. thoracico-dorsahs 

 of the selachians (Pitzorno, loc. cit.), and a ventral branch 

 (a. thv.) which is probably the a. thoracico-ventralis of those 

 forms. Its principal remaining branches supply the muscula- 

 ture of the fin. 



ARTERIES TO THE KIDNEY 



The arteries that directly supply the dorsal side of the kidney 

 (fig. 18, a.re.) and swim-bladder are numerous small vessels 

 that arise irregularl}^ along the ventral side of the aorta. Within 

 the kidney there is also sometimes developed a longitudinal 

 stem of greater size. The finer anatomy of these vessels in 

 relation to the renal tissues was not studied. 



THE COELIACO-MESENTERIC ARTERY 



The coeliaco-mesenteric artery (figs. 15, 19, a. co me.) arises 

 from the dorsal aorta between the levels of the anterior end of 

 the coelom and the posterior margin of the pronephros. Enclosed 



