THE ELASMOBRANCH FISHES 



203 



part. The posterior part is first found al)out halfway between the pectoral and 

 pelvic segments and continues from this point posteriorly almost to the tip of 

 the tail. In the region of the dorsal lobe of the caudal fin the dorsal cutaneous 

 vein is double, and around the dorsal fin right and left dorsal cutaneous veins 

 form a loop from which a strong intercommunicating branch passes to join the 

 lateral cutaneous vein. From the unpaired vein just back of the loop a medium 



Fig. 188. Sinus venosus opened, Heptanchus maculattis. (Euth Jeanette Powell, del.) 



a.c, anterior cardinal; au., auricle; h.v., hepatic vein; i.j., inferior jugular vein; p.c.s., 

 postcardinal sinus; sa., sinu-auricular valve; s.cl., subclavian vein; s.v., sinus venosus; v., 

 valves of anterior cardinal sinus. 



deep vein (m.v.) passes to the right of the spinal column to join the caudal 

 vein (cd.v.). The anterior part of the dorsal cutaneous vein ends anteriorly 

 in a V-shaped sinus over the brain case. 



The lateral cutaneous vein (Lev., fig. 189) runs directly under the skin, 

 parallel with and ventral to the lateral line groove. It extends from the middle 

 region of the caudal fin forward, and joins the subscapular sinus near its tip 

 (fig. 187). In its course forward it receives numerous segmentally arranged 

 cutaneous branches, and in the region of the dorsal fin it has strong intercom- 

 municating branches which join the cloacal vein (cl.v.) of the lateral ab- 

 dominal system. 



Fig. 189. Cutaneous veins, Heptanchus macidatus. (Helen Hopkins, orig.) 

 cd.v., caudal vein; cJ.v., cloacal vein; l.c.v., lateral cutaneous vein; 77!.^;., median unpaired 

 vein ; p.d.c, posterior dorsal cutaneous vein ; p.v.c, posterior ventral cutaneous ; s.sc.v., sub- 

 scapular vein. 



The ventral cutaneous vein lies in the subcutaneous tissue in the midventral 

 line. In the region of the anal fin it forms a loop and like a V its right and left 

 branches run backward on the caudal fin. The posterior part of the vessel 

 empties into the cloacal vein (cLv.) and the anterior segment of this vein joins 

 the coracoid vein (co.v., fig. 187) . 



