BLOOD-VASCULAR SYSTEM OF THE LORICATI 



49 



larger leftfharynx artery (PL II, fig. 12; L.Phar.A.) sup- 

 plies the pharynx and similar muscles on the left side. Soon 

 after the left pharynx artery leaves the main stem it gives 

 off the large coronary artery (Pis. I and II, figs i and 12 ; Cor.- 

 A.) for the heart. For some little distance this vessel runs 

 along the dorsal surface of the ventral aorta and then divides 

 into a dorsal and a ventral trunk. The dorsal coronary artery 

 (PL II, fig. 12 ; D.Cor.A.) continues along the dorsal surface of 

 the ventral aorta and bulbus arteriosus to the heart as the prin- 

 cipal vessel. Usually this vessel bifurcates in the region of the 

 conus arteriosus, one branch penetrating directly into the mus- 

 cular layer of the ventricle, while the other is a superficial vessel, 

 distributing itself over the dorsal surface of the ventricle ; or 

 sometimes both may be superficial vessels. It is probable that 

 these vessels also supply the auricle, although I have never 

 been able to trace them further than the ventricle. Each of 

 these vessels gives off a small artery, which encircles the bul- 

 bus and anastomoses on the ventral side with the ventral coro- 

 nary artery, and from this circular artery several small vessels 

 are given off to the bulbus and the ventricle. The ventral 

 coronary artery (PL II, fig. 12 ; V.Cor.A.), which is much 

 smaller than the dorsal vessel, also runs caudad in the outer 

 coat of the ventral aorta, but it supplies only the ventral walls 

 of the ventral aorta and the bulbus. None of its branches 

 reaches the ventricle. In Scorj^cenichthys the pharynx arteries 

 arise as separate arteries from the second pair of efferent 

 branchial arteries, and the coronary artery comes from the left 

 pharynx artery, close to its point of origin from the efferent 

 branchial vessel. 



The Ventral Artery (Pis. I and II, figs, i and 12 ; Ven.A.) 

 is the largest of any of the vessels arising from the ventral 

 ends of the efferent branchial arteries. In Opkiodon this ves- 

 sel has its origin from the ventral union of the second and third 

 pairs of efferent branchial arteries. This does not appear to 

 be the common arrangement among other bony fishes ; in Hex- 

 agranimos, ScorpcBnichthys , and Sebastodcs the ventral artery 

 has its source from the second pair of efferent branchial vessels. 

 Continuing caudad along the ventral surface of the pericardial 



Proc. Wash. Acad. Sci., June, 1905. 



