CIRCULATORY SYSTEM OF ELASMOBRANCIS. 449 
about 5 mm.,and it quickly divides into two main branches, 
a right and a left, one feeding each lobe of the liver. 
Text-figure 3. 
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Diagram of the factors of the Hepatic Portal System in Scyllium cantcula, 
viewed from the ventral side. 
For explanation of lettering see p. 464. 
1. The Posterior Intestinal Vein [ Pl. I1., P.I.] commences as a 
small vein on the ventral side of the rectal gland, and then, 
turning sharply upon itself, passes along the dorsi-lateral wall of 
the intestine to a point just posterior to the caudal end of the 
pancreas. At this place, marked also as the point at which the 
anterior mesenteric artery reaches the gut-wall, the posterior in- 
testinal vein receives a fairly large factor from the anterior end 
of the intestine, and then it runs freely to join the posterior 
lieno-gastrie vein in the pancreas. During its course along the 
intestine the vein receives a number (usually eight) of well- 
marked paired tributaries, whose position on the outside of the 
intestine marks the line of insertion of the folds of the spiral 
valve within. 
