168 



THE ELASMOBRANCH FISHES 



gland where it divides, the anterior branch joining the dorsal intestinal artery 

 to which reference has been made. The posterior part supplies numerous 



branches to the rectal gland and rectum. 



AETEEIAL SUPPLY TO EXTREMITIES 



Fig. 157. The dorsal aorta and its 

 branches, Heptanchus maculatus. 

 (Marie Weldt, orig.) 



a.dl., anterior dorsolateral artery; 

 a.l., anterior part of lateral artery; 

 hr.a., brachial artery; ce.. coeliac axis; 

 co.a., coracoid artery; ic, intercostal 

 artery; il., iliac artery; i.m., inferior 

 mesenteric; od.a., oviducal artery ; p.dl., 

 posterior dorsolateral artery; p.l., j)os- 

 terior part of lateral artery; r., asym- 

 metrical rectal artery ; s.cl., subclavian 

 artery ; sg., segmental artery ; s.m., su- 

 perior mesenteric artery. 



The arterial supply to the extremities in- 

 cludes a pair of subclavian arteries (s.cl., 

 fig. 157) carrying blood to the pectoral 

 fins, and a pair of iliac arteries (il.) lead- 

 ing toward the pelvic fins. 



The subclavian arteries in Heptanchus 

 maculatus are unusual in that they often 

 are no better developed than are the com- 

 mon intercostals (ic). They pass from the 

 dorsal aorta near the union of the last ef- 

 ferents and out toward the pectoral re- 

 gion. A short distance out each subclavian 

 gives off a dorsolateral artery, one rela- 

 tively large division of which passes for- 

 ward (a.dl., fig. 157) and one backward 

 (p.dl.). From about this point a smaller 

 artery passes dorsally supplying the area 

 posterior to the scapula. The brachial ar- 

 tery (hr.a.) leaves the subclavian and con- 

 tinues through a foramen in the pectoral 

 girdle to the pectoral fin. From the 

 brachial foramen the subclavian is con- 

 tinued forward by a larger brachioscapu- 

 lar vessel (see also hsc, fig. 169) to join 

 the coracoid artery (co.a., fig. 153) at a 

 place where it meets the lateral (abdomi- 

 nal) artery (a.l.). The coracoid in turn 

 joins the median ventral unpaired artery 

 (see fig. 153), described with the hypo- 

 branchial system. 



Arising from the brachioscapular ves- 

 sel is a branch (nit., fig. 153) , which passes 

 along the metapterygium of the pectoral 

 fin. The lateral artery (a.l., figs. 153 and 

 157) is a continuation of the coracoid; it 

 passes backward, hidden by the lateral 

 abdominal vein, to join the iliac artery 



(il.) from the posterior region. Also leav- 

 ing the coracoids, but farther anterior than the origin of the lateral, is the pos- 

 terior coronary artery (cr.p., fig. 153), which has been previously described. 



