THE ELASMOBRANCH FISHES 



189 



rately i'l-om the dorsal aorta. In such, the posterior intestinal arises anterior 

 to and crosses over the anterior gastro-i)anereaticos])lenic. This condition is 

 characteristic of many ty])es of which it should be said that no true superior 

 mesenteric artery exists. 



Fig. 177. Dorsal aorta and its segmentals. A. ScyUnim. (Prom Carazzi.) 

 B. Dasyatis. (Blanche Lillibridge, orig.) 

 hr.a., braeliial artery; ce., eoeliae axis; cL, cloacal branch; da., branch to clasper; d.a., 

 dorsal aorta; d.l., dorsolateral artery; f.in., iliac artery; mt.a., metapterygial artery; o.d., 

 oviduct; od.a., oviducal artery; p.i.a., posterior intestinal artery; p.l., posterior lateral 

 artery; pr.a., propterygial artery; r., rectum; s.cL, subclavian artery; s.m., superior mesen- 

 teric; t*. v., urinary vesicle. 



The anterior gastro-pancreaticosplenic (a.gps.) is contrasted with the pos- 

 terior gastro-pancreaticosplenic {p.gps.), previously described, by its supply- 

 ing a more anterior (proximal) segment of the digestive tract. While, as we 

 have seen, the posterior artery of this name is in relation to the pyloric part 



