The Sturgeon more closely resembles the Elasmobranchs. The hyoidean gill is supplied by an afferent branchial artery from the ventral aorta, and its efferent vessel joins the corresponding trunk from the holobranch of the first branchial arch. A hyoidean artery supplies the spiracular pseudobranch, the efferent vessel of which contributes to the blood-supply of the brain and the eye, and probably represents an anterior carotid. _Lepidosteus_[384] offers a singularly interesting transition from the {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 supplied 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 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. [Illustration: FIG. 197.—Blood-vessels of the spiracular pseudobranch and the hyoidean gill in _Lepidosteus_. _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.a^{1-4}_, efferent branchial vessels; _hy.a_, hyoidean artery; _hy.h_, hyoidean gill; _hy.ps_, spiracular pseudobranch; _v.a_, ventral aorta. (From F. W. Müller, after Johannes Müller.)] 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 pseudobranch. The latter is now supplied by a "hyoidean" artery, which has its origin from the ventral end of the efferent {336}branchial artery of the first branchial arch, the corresponding efferent trunk forming an ophthalmic artery, and passing to the choroid gland of the eye (Fig. 199). Both the proper afferent and efferent arteries of the hyoidean hemibranch either disappear or, as in the Cod (_Gadus morrhua_), the efferent artery may be represented on each side by an anastomosis between the hyoidean artery and the cephalic circle. Hence, the "hyoidean" artery of Teleosts corresponds to the one which has a similar origin in _Lepidosteus_. A brief description of the remaining efferent branchial arteries and their derivatives in the Cod (_Gadus morrhua_) will illustrate the condition of these structures in a well-known Teleost.