A treatise on zoology . t fromthe epichordal lobe (Fig. 46). The radials of the paired fins arestill more i-educed than in the Chondrostei. The clavicle is lost,its place being taken by the cleithrum, and the endoskeletal pectoralgirdle is relativeh small (Fig. 241). The maxilla generally bothacquires a free posterior end and bears one or two supra-maxillary bones. In the two first sub-orders the lower jaw is stillprovided with a dentary, angular, supra-angular (coronoid), splenial,and articular (Figs. 237-240). Of the inferior gulars only a single HOLOSTEI 323 median one may persist (Amioidei
A treatise on zoology . t fromthe epichordal lobe (Fig. 46). The radials of the paired fins arestill more i-educed than in the Chondrostei. The clavicle is lost,its place being taken by the cleithrum, and the endoskeletal pectoralgirdle is relativeh small (Fig. 241). The maxilla generally bothacquires a free posterior end and bears one or two supra-maxillary bones. In the two first sub-orders the lower jaw is stillprovided with a dentary, angular, supra-angular (coronoid), splenial,and articular (Figs. 237-240). Of the inferior gulars only a single HOLOSTEI 323 median one may persist (Amioidei and some Teleostei). The hyoidarch IS formed of five cartilages : hyomandibular, interhyal, hypo-hyal, and basiliyal; but the ceratohyal always ossifies in a maininferior ceratohyal and a smaller superior epihyal. Sincehowever, the interhyal (stylohyal) probably corresponds to the epi-branchial in the posterior arches, and should be called epihyal, itIS possible that the epihyal ossification below it does not represent. Fig. longitudinal section tlirough the head of Sahw salar, L. (Modified, after Bruch )k1, ^^ arteriosus; 66, basibranchial, , branchiostegal membrane- itt^\ ^r^^l^:VfT ^^y^V-® = ?• ^-ertebral centrum ; d, dentary ; , dorsal aorta;nnJfa^Tl ^f-y ^ ^? ?• ^1 ^«=li ; ^?^- enlarged neural spine ; ^rio^^iJ IZf °P ? T^ ^ Pecardium ; pa, parasphenoid ; pw, septum betweennhHnnP ,^L^ abdommal coelom ; , anterior vertical semicircular canal ; , superioroblique mubcle of eye ; sp, neural spine ; , sinus venosus ; nh, urohyal ; v, ventriclevalves separate Its cavity from tiiat of atrium above and bulbus in front ; m, va^us , ventral aorta ; vm, rectus muscle of eye in eye-muscle canal ; vo, vomer. an element found separate in the lower forms (Fi^s. 239, 322,331). The basibranchials are usually well represented, though«ften the two last, and sometimes others, are fused together. InLepidosteus and most Teleost
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