ao VASCULAR SYSTEM 335 
Elasmobranch to the Teleost. As indicated in the preceding 
chapter, this Fish possesses both a hyoidean gill and a spiracular 
pseudobranch (Figs. 197 and 198). The hyoidean gill is sup- 
plied by an afferent artery direct from the ventral aorta, but the 
proper efferent vessel of the gill, which primitively joined the 
dorsal aorta, is suppressed, and the blood is collected into a 
vessel, which, like the hyoidean artery in Elasmobranchs, becomes 
the afferent artery of the spiracular pseudobranch. The latter 
Fia. 197.—Blood-vessels of the spiracular pseudobranch and the hyoidean gill in Lepi- 
dosteus. af.a, ef.a, Afferent and efferent vessels of the hyoidean gill; af.ps.a, 
ef.ps.a, afferent and efferent vessels of the spiracular pseudobranch; ca, carotid 
(posterior) ; d.a, dorsal aorta ; ef.b.a1~4, efferent branchial vessels ; hy.a, hyoidean 
artery ; hy.h, hyoidean gill; hy.ps, spiracular pseudobranch ; v.a, ventral aorta. 
(From F. W. Miiller, after Johannes Miiller.) 
artery unites, however, with a second hyoidean artery derived 
from the efferent branchial vessel of the first branchial arch, and 
represents the artery termed “hyoidean” in Teleosts. The 
efferent vessel from the spiracular pseudobranch joins an internal 
branch from the carotid artery, and then distributes its blood 
both to the eye and the brain. 
In Teleosts, as already mentioned in a preceding chapter, 
it is probable that the hyoidean hemibranch is suppressed, the 
so-called hyoidean pseudobranch being a spiracular pseudo- 
branch. The latter is now supplied by a “hyoidean” artery, 
which has its origin from the ventral end of the efferent 
