THE ELASMOBRANCH FISHES 



179 



tyi)e. Tn Cdirluirids I it f oralis one is dorsal and the other ventral. In Zygaena 

 two are ventral and a third is dorsal. 



In HexancJius corinus the median stem of the coracoid artery (co., fig. 

 169) arises from the left median hyi)obranchial and is continued posteriorly 

 by the coracoid artery (co/). The coracoid is continued as the lateral (ab- 

 dominal) artery which follows the course of the lateral abdominal vein. From 

 the lateral (abdominal) artery 

 the brachioscapular artery {bsc, 

 fig-. 169) carries a large supply- of 

 blood to the pectoral area and 

 joins the subclavian at a point 

 where the brachial artery (br.) is 

 given off to the fin. 



From the median hyprobran- 

 eliials, or from the last commis- 

 sural, the pericardial (pc, fig. 

 166b) and the coronary arteries 

 (cr.l.) may arise, and near the 

 origin of pericardials and coro- 

 naries in the rays, the coracoid 

 artery (co.a.) joins the last com- 

 missural {Dasyatis, fig. 167). In 

 Carcharias littoralis a branch, 

 designated by Parker and Davis 

 as the epigastric, arises from the 

 median unpaired hypobrancliial. 



The pericardial, as in Heptan- 

 chus, goes to supply the dorsal 

 pericardial wall, and to furnish 

 branches to the oesophagus and 

 one or more epigastric arteries to 

 the dorsal side of the stomach. An interesting condition obtains in Lamna cor- 

 nuhica (Burne. 1923) in which the pericardials, after having traversed the 

 "supra-hepatic retia," supply practically the whole of the blood to the 

 digestive tract. 



The coronary arteries {cr.l., figs. 166b and 167) in the Elasmoliranchs are 

 unusually well developed. They may consist of a median ventral artery aris- 

 ing from the ventral type of commissure and a single dorsal arising from the 

 dorsal type as in Carcharias littoralis. Or they may consist of a pair of vessels, 

 the left one of which may go to the ventral side of the conus and ventricle, and 

 the right to the dorsal side. In Heterodontus two pairs of coronaries are pres- 

 ent, one of which is dorsal, the other ventral. In the rays, as in Heptanclius, a 

 posterior pair of coronaries {cr.p., fig. 169) arises from the coracoid arteries 

 and runs forward to the sinus venosus and ventricle. These coronaries are 

 especially interesting in Dasyatis. While the right posterior artery extends 



Fig. 169. Eelations of coracoid to lateral (ab- 

 dominal) artery, Hexanchus corinus, ventral 

 view. (From Keys.) 



CO., median stem of coracoid artery; co.', cora- 

 coid artery; br., brachial artery; hsc. brachio- 

 scapular artery; cr.p., posterior coronary ar- 

 tery; l.a., lateral (abdominal) artery; l.a.v., 

 lateral abdominal vein; .s.cl.v., subclavian vein. 



