THE ELASMOBRANCH FISHES 



187 



tirely absent {Dasyatis, fig. 175). The gastric arteries follow much the same 

 plan in the Elasniobranchs generally as lias been descril)ed for Heptanchus. 

 In certain forms, however, a dorsal gastric may be well developed. 



The hepatic artery may arise as a single trunk, Heptanchus, or a hepatic 

 l)ranch may be given off from the anterior intestinal artery, as in Mustelus ant- 

 arcticus (fig. 173b). Occasionally a second hepatic branch may be given off 

 from the ventral gastric in Triakis. The hepatic artery (or arteries) supply 

 twigs to the ductus choledochus, to the sail bladder, and to the liver. 



Fig. 175. Arteries to the digestive tract, Dasyatis dipterura, ventral view. (Blanche Lilli- 

 bridge, orig.) 



Fig. 176. Duodenal supply, Dasyatis dipterura, dorsal view. (Blanche Lillibridge, orig.) 

 a.g., anterior gastric artery; a.g.v., anterior gastric vein; a.gps., anterior gastro-panerea- 

 tieosplenic artery; a.gs., anterior gastrosplenic artery; a.i.a., anterior intestinal artery; 

 ce., coeliac axis; c.s., cardiac stomach; d.i.a., dorsal intestinal artery; d.ch., ductus choled- 

 ochus; d.i.v., dorsal intestinal vein; du., duodenum; gd., gastroduodenal artery; h., hepatic 

 artery; h.p., hepatic portal vein; i.a., intraintestinal artery; oe., oesophagus; p.gps., pos- 

 terior gastro-pancreaticosplenic artery ; p.gs., posterior gastrosplenic artery ; p.gs.v., pos- 

 terior gastrosplenic vein; p.i.v., posterior intestinal vein; pn., pancreatic branch; pn}~'^, 

 dorsal and ventral lobes of pancreas; py., pylorus; s.m., superior mesenteric artery; spA., 

 valvular intestine; v.g., ventral gastric artery; v.g.v., ventral gastric vein. 



