178 ' JEREMIAH S. FERGUSON 



artery passes backward on either side of the median line beneath 

 the dorsal portion of the pericardium at the lateral margin of the 

 cartilaginous floor of the pharynx formed by the basi-branchial 

 cartilage ; after anastomosing with its fellow of the opposite side 

 beneath the apex of the cardiac ventricle it distributes its ter- 

 minal branches to the wall of the esophagus and stomach near the 

 cardia (figs. 5 and 6). 



From the loop at the ventral end of the fourth branchial arch 

 a very small anastomotic branch (less frequently arising as in fig. 

 6, hypohr') passes backward along the lateral wall of the pericar- 

 dium and penetrating between the precaval sinus and the coracoid 

 arch anastomoses with the subclavian artery just prior to its 

 division into the brachial (axillary) and the lateral (or hypo- 

 gastric, a large artery lying parallel to the lateral vein. This anas- 

 tomotic branch is undoubtedly that which T. J. Parker ('86) 

 describes as the hypobranchial, which, according to his descrip- 

 tion receives blood from the subclavian and supplies the coro- 

 nary arteries and whole hypobranchial system. Such is not the 

 case, however, in any of the species I have studied and Hyrtl 

 ('72) in his careful study of various species of the Selachii did 

 not so find it, nor did Parker and Davis ('99). The hypobran- 

 chial is a very small artery, so small that its connection with the 

 median hypobranchial is scarcely traceable, and in some individuals 

 is entirely wanting (fig. 5), there being in these cases a small 

 branch from the subclavian and a similar vessel from the median 

 hypobranchial which follow the usual course but never unite, the 

 subclavian branch distributing its blood to the muscles while the 

 anterior division supplies the lateral pericardial wall and the adja- 

 cent muscles in front of the coracoid arch. Certainly where the 

 vessel is wanting the flow of blood can not be in the direction 

 indicated by T. J. Parker. Parker and Davis ('99), as already 

 quoted, found the hypobranchial artery insignificant, though they 

 did not record its absence. 



If the median hypobranchial artery of Mustelus be injected the 

 major portion of the fluid passes into the coronary arteries and 

 thence through the coronary veins to the sinus venosus and auricle, 

 while at the same time very little passes through the hypobran- 



