3^S 



THE DOGFISH. PHYLUM CHORDATA 



cleft, having no gill on its hinder side, has an efferent vessel on 

 its front side onl3^ and all the blood of this vessel passes by the 

 horizontal vessel into that of the gill in front. From the dorsal 



oif.o. 



Fig. 248. — The forepart of a dogfish, dissected from the ventral side, to show the 

 dorsal arterial system, the olfactory organs, and certain structures in the 

 orbits. The middle part of the floor of the mouth has been removed. 



■t.b.a , Afferent branchial arteries ; coe.a., coeliac artery ; d.ao., dorsal aorta ; e.b.a., efferent branchial 

 arteries ; en., nostril ; epibr., epibranchial artery ; h.m., hyomandibular cartilage ; i.e., internal carotid 

 foramen ; inf., infundibulum ; M.c, Meckel's cartilage in lower jaw ; o.i., inferior oblique muscle ; 

 O.S., superior oblique muscle ; olf.o., olfactory organ ; orb., orbital or ' external carotid ' ; p.d.a., 

 prolongation of aorta ; r.c.a., carotid root ; sc, scapula ; scl., subclavian artery ; sk., skull ; sp., spiracle ; 

 sp.a., spiracular artery; V.md., V.mx., mandibular and maxillary branches of fifth nerve ; //., optic 

 nerve. 



end of each of the complete loops arises a vessel known as an 

 epibranchial artery, which runs backwards and inwards on the 

 roof of the pharynx to join the median dorsal aorta opposite 

 to its fellow of the other side. From the dorsal end of the first 

 efferent branchial artery, just outside the origin of the first 



