226 Transactions. — Zoology. 



walls, several small pancreatic veins from the right lobe of the pancreas, 

 and a large anterior splenic vein (a. sp. v) from the spleen, as well as the 

 intra-intestinal vein mentioned below : the mesenteric receiving transverse 

 veins from the intestinal walls, and a large lieno-gastric vein (l.g.v) which is 

 formed mainly by a longitudinal vein from the left side of the stomach and 

 receives also veins from the spleen. After receiving the lieno-gastric, the 

 mesenteric vein runs through the left lobe of the pancreas, receiving veinlets 

 from it, and unites with the duodenal immediately anterior to that gland. 

 The common portal vein passes dorsal to the bursa Entiana and along the 

 right side of the stomach, parallel with the coeliac artery and bile-duct, 

 receiving as it goes the veins for the right side of the stomach. 



In the paper already referred to on the spiral valve of the skate, I 

 described that structure as being supplied entirely by the mesenteric arteries 

 and veins, but stated that the bursa Entiana received a special blood-supply 

 in the duodenal vessels. Owing, however, to imperfect injections, I missed 

 one important point. The spiral valve of Elasmobranchs has, in fact, a double 

 blood- supply : vessels from the transverse branches of the mesenteric — and 

 ia Scymnus, Mustelus, etc., of the duodenal — arteries and veins pass inward 

 to it, but in addition to these its free edge encloses an artery and vein which 

 may be traced forwards into the duodenal artery and veins respectively. The 

 vein in question has been shown by Balfour* to be formed from part of the 

 sub-intestinal vein of the embryo. As far as I know no name has been 

 given to it as it occurs in the adult, and as it corresponds to part only of 

 the sub-intestinal vein, and is known to persist only in the spiral valve of 

 Cyclostomata and Elasmobranchs, I propose to call it the intra-intestinal vein, 

 and the artery accompanying it the intra-intestinal artery. It attains its 

 greatest dimensions in those sharks which possess a scroll-valve, such as 

 Zygoma, Carcharias, and Galeocerdo,\ but is almost equally conspicuous, as 

 I have lately found, in Mustelus antarcticus and in Callorhynchus antarcticus, 

 both of which have an ordinary spiral valve, although that of the Holo- 

 cephali shows transitional characters to the scroll-valve. J In Scymnus, as in 

 the skate, the intra-intestinal vein is quite small and easily missed in 

 injecting. 



But tbe most interesting point in the vascular system of Scymnus is the 

 presence of a large lateral vein, having the same essential relations as the 

 vein I described in the skate. § Posteriorly it is connected with the veins 

 from the pelvic fin, from the anterior border of which it passes forwards 



* Comparative Embryology, vol. ii., p. 535. 



t See Duvernoy, Ann. des Sci. Nat., ser. ii., 1835, t. iii. 



I See " Spiral Valve of Skate," loc. cit., p. 



§ " On the Venous System of the Skate," Trans. N.Z. Inst., vol. xii., pp. 413-18. 



