BLOOD-VASCULAR SYSTEM OF TIIK LORICATI 69 



supply for the viscera of Sco7'fcBnichthys is most like Op/iwdon, 

 and Scbastodcs most like the ordinary Acanthopterygian fishes. 



The origin of the co^liaco-mesenteric trunk is the same for all 

 4 genera studied, but as regards the branching of the coeliac 

 and especially the mesenteric, there is considerable variation. 



Cccliac Artc7'y. — In Hcxag7-aminos the coeliac branches off 

 from the cosliaco-mesenteric trunk much further caudad than is 

 the case with the other 3 genera ; in fact, the coeliac and the 

 left gastric are given off together. In all 4 genera the coeliac 

 terminates by dividing into the 2 pyloric casca arteries, but in 

 Ophiodon only does a pyloric ca^ca artery supply the posterior 

 part of the stomach. In Scbastodcs the left hepatic arteries 

 (PI. IV, fig. 32 : L.Hep.A.) arise in a similar manner to 

 the corresponding vessels of Ophiodon, except that the pos- 

 terior left hepatic artery is much larger than in Ophiodon ; while 

 in ScorpcBnichtJiys and Hexagrammos, strange' to say, the left 

 hepatic arises from the right gastric, but in Hexagramnws it 

 comes into such close contact with the coeliac that at first one 

 might be led to believe it arose from the coeliac or at least anas- 

 tomosed with it. In Hexagrammos only does the intestinal 

 arter3',o) arise from the coeliac as in Ophiodon ; in Scorpcenich- 

 thys and Scbastodcs it is a branch from intestinal artery^i^. 



Mesenteric Artery. — The right and left gastric arteries 

 respectively are essentially the same in all 4 genera. How- 

 ever, since there are so many variations in the branching of the 

 right gastric, the distribution of intestinal artery^i), and the addi- 

 tional air-bladder and anterior spermatic arteries in Sebastodes^ 

 it seems advisable to describe in detail the distribution of the 

 mesenteric artery for each of the above genera. 



Mesenteric Artery in Scorpcenichthys (PI. IV, fig. 29 ; a fork 

 of Coe. Mes.A.). — After giving off the left gastric artery, the 

 mesenteric artery separates into the right gastric artery (fig. 

 29, R.Gas. A.) and the intestinal artery(i)(fig. 29 ; Int. A.^d). The 

 former gives off the left hepatic artery (figs. 29 and 30: L.- 

 Hep.A.) and the latter follows along the stomach for a short 

 distance, giving off a small branch to a small gland-like body, 

 marked 0-, and the splenic artery (PI. IV, fig. 29; Spl.A.), but 

 before entering the spleen this vessel sends off a posterior gas- 



