RELATION OF ARTERIES IN COMMON GANOIDS 395 



are better developed in Scaphirhynchus than in the skates that 

 have been described. The conunon trunk {ch) usually divides 

 into coronary and hepatic divisions, each of which may again 

 divide before entering its respective organ. The posterior coro- 

 nary artery supplies the base of the heart and the aortic bulb; 

 the anterior hepatic branches supply the very abundant lymphoid 

 areas within the anterior part of the liver. 



The apex of the heart may be supplied by a typical arteria 

 apicis cordis (ac) such as Spalteholz ('08) found in certain turtles 

 and lizards. This observation is of interest since Spalteholz 

 thought the vessel did not occur in fish, birds or mammals. In 

 the Scaphirhynchus used for the accompanying sketch the ar- 

 tery was as well developed as in the case of some of the turtles 

 shown in Spalteholz's own figures. I have not been able, how- 

 ever, to demonstrate it in all cases, so the vessel is probably 

 variable in its occurrence. 



The points in which Scaphirhynchus departs from the typical 

 condition found in skates are, briefly, the greater development of 

 posterior coronary arteries with the associated anterior hepatic 

 vessels, the absence of anterior coronaries, and the potentiality 

 of an arteria apicis cordis. 



POLYODON 



The same hepatic and coronary arteries found in Scaphirhyn- 

 chus are present in Polyodon, except for the arteria apicis cordis 

 which has not been observed. The relation of these vessels to 

 the heart and liver are essentially the same in the two species, 

 but the origin of the hepatico-coronary trunk is quite different. 

 In Polyodon this vessel arises from the fourth efferent branchial 

 artery, a fact which it was found difficult to interpret when the 

 arteries of this fish were first described. 



This peculiar arrangement is easily explained bj' reference to 

 the condition found in Scaphirhynchus. In the latter (fig. 1) 

 there is an artery arising from the fourth aortic arch which sup- 

 plies a part of the oesophagus and the region about the pericar- 

 dium. In Polyodon this vessel has anastomosed with the he- 



