RELATION OF AKTEKIES IN COMMON (iANOlDS 898 



have pointed out. that the (joniiectioii between the siibchivian 

 and hypobranchial arteries is generally shght or actually lac^king. 

 This is interpreted to mean that the two systems are essentially 

 distinct with (mly secondary anastomoses. This being the case, 

 the posterior coronary arteries of skates are derived from the sub- 

 clavian artery, the anterior coronaries from the true hypobran- 

 chial system. Parker and Davis ('99) designated the branch of 

 the subchu'ian from which the posterior coronary arises as the 

 coracoid. They also differentiated clearly between median and 

 lateral h> po-branchial arteries and recognized the existence in 

 Carcharias and other forms of dorsal and ventral anterior coro- 

 naries. 



It will be apparent from the foregoing that a discussion of the 

 morphology of the coronary and hepatic arteries of ganoids will 

 involve some consideration of the subclavian and hypobranchial 

 arteries. The accompanying schematic drawings show the es- 

 sential relations of these vessels in the fishes studied. 



The i)rincipal branches of the subclavian artery are faii'Iy con- 

 stant. After reaching the le\^el of the lateral line the main trunk 

 gives rise above to a dorsal and below to a \'entral superficial 

 branch to the lateral body musculature. Following Pitzorno ('05), 

 these may be designated as Rr. thoracico-dorsalis and thorac- 

 ico-ventralis. Between these two vessels arise branches to the 

 abductor and adductor muscles of the fin and a branch which 

 runs forward beneath the heart to supply the Aim. coracoarcualis 

 and pharyngoclaviculares. This is the coracoid artery of Parker 

 and Davis (/. c). 



The hypobranchial system of vessels is somewhat rudimentary 

 and highly variable. It does not lend itself i-eadily to a general 

 description. 



The condition found in skates is most closely approached by 

 Scaphirhynchus. This form will therefore be described hrst. 



s('Al'HIl{ll^ xcins 



in S('a])hirhynchus anterior and ]jos1(M'i()i' h(^])ati(' and ])ost(M-i()r 

 corojiaiy arteries are present. 1 have not found anterioi- coi'o- 

 nai'ies. The coeliaco-mesenteric artery passing down on the 



