The American journal of anatomy . n Polyodon this vessel arises from the fourth efferent branchialartery, a fact which it was found difficult to interpret when thearteries of this fish were first described. This peculiar arrangement is easily explained bj reference tothe 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- ;i96 C. H. DANFOKTtI patic and coronary vessels and become their main trimk. Theori
The American journal of anatomy . n Polyodon this vessel arises from the fourth efferent branchialartery, a fact which it was found difficult to interpret when thearteries of this fish were first described. This peculiar arrangement is easily explained bj reference tothe 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- ;i96 C. H. DANFOKTtI patic and coronary vessels and become their main trimk. Theoriginal hepatico-coronary trunk (ch) is now reduced to a smallbranch connecting the coronary artery with the subclavian. Itwas originally interpreted as merely a secondary anastomosis. As in Scaphirhynchus no anterior coronary arteries are might be interpreted as a rudimentary dorsal coronary islost on the ventral aorta before reaching the heart. Polyodondiffers from Scaphirhynchus chiefly in that the origin of the he-. md. coca. va. cp. ha. thv add. Iiv hp Fifr. 2 Tlie coioiiaiy and licpalic artiiics of Polyodon. Letters as in Hgurc ] patico-coronary trunk is transferred from the coracoid branchof the subclavian to the dorsal part of the fomth efferent bran-chial artery. :iii)()SiEiTs In Lepidosteus, posterioi- hepatic and anterior coronary ar-teries alone are present. The latter arise from a vessel whichcomes off on the right from the large oesopliageal trunk, whicharises in turn from the subclavian artery. The anterior coio-nary arteries arise from a short median hypobranchial which de-rives its supply partly from the A. niaiidibularis {md) and partlyfiom a commissural artery at the level of the second gill. Thesetwo vessels unite laterally and the resulting common trunk reaches RELATION OF AUTERIEft IN COMMON GANOTDS :i\)7 the median line below the aortu. The coronary arteries, whichfollow the aorta back, give rise to branches that may be definitehi
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Keywords: ., bookauthorwi, bookcentury1900, bookdecade1910, booksubjectanatomy
