THE ELASMOBRANCH FISHES 



199 



182-184) from the hyoidean demibranch and from all the holobranchs. Pos- 

 teriorly, the anterior cardinal sinus drops suddenly downward into the duet 

 of Cuvier (f7.r., fig. 183). 



A second vessel, dorsal to the brancliial region but nearer the middle line, is 

 the Danielian sinus (d.s., figs. 182 and 183) discovered by Mast Wolfsohn. 

 Anteriorly this sinus extends almost to the vagus foramen and posteriorly it 

 reaehes practically to the end of the anterior cardinal sinus. The anterior ex- 

 tremity ends in a blind sac (hs.) and similarly the posterior extremity may 

 end l)lindly. The Danielian sinus is connected with the anterior cardinal by 

 numerous openings (ap., fig. 183) the most anterior of which is near the en- 



Fig. 183. Danielian sinus, Hci^ianchus maculatus. (Eiith Conrad, orig.) 

 ap., apertures connecting anterior cardinal (a.c.s.) and Danielian sinuses (d.s.) ; 1)8., 

 blind sacs leading from Danielian sinus; d.c, entrance to duct of Cuvier; nu., nutrient 

 vessels ; po.o., posiorbital process. 



trance of the hyoidean vein. Other openings (aj).) between the anterior cardi- 

 nal and Danielian sinuses, posterior to this point, are arranged more or less 

 segmentally as may be seen by lifting up the vagus nerve. 



The inferior jugular vein (i.j., fig. 184) drains the ventral area of the phar- 

 ynx and extends as an enlarged vein or sinus back to the heart. Anteriorly it 

 receives a tributary from the symphysis of the lower jaw (smt.) and another 

 from the thyroid region (th.v.). It next receives the hyoidean vein or sinus 

 (h.s.) and. at regular intervals back of this, ventral nutrients (nv.) which are 

 continuous with the dorsal nutrients of the anterior cardinal. Notwithstand- 

 ing the fact that it receives veins from all the holobranchs, the inferior jugu- 

 lar decreases in caliber in its course backward. Near its termination it curves 

 laterally and then passes backward to enter the duct of Cuvier just mediad of 

 the entrance of the subclavian vein (fig. 188) . 



VEINS OF TAIL 



The caudal vein (cd.v., fig. 185) passes forward in the haemal canal of the 

 tail, and back of the cloaca divides into the renal portal veins (r.j).) . It receives 

 branches from the dorsal and posterior ventral cutaneous veins (fig. 189) and 

 numerous segmental veins from the tail; other segmentals join the renal 

 portals as they pass along the dorsolateral margins of the kidney. The ventral 

 rami of the segmental veins receive the blood from the musculature of the 

 ventral lobe of the caudal fin, and each dorsal ramus collects venous blood 

 from dorsal musculature and from the spinal cord. The renals finally break up 

 into a net in the tissues of the kidney. 



