Elements of the comparative anatomy Elements of the comparative anatomy of vertebrates elementsofcompar00wied Year: 1886 THE SKULL. In other points, however, they differ considerably from all these ; and it is clear that the last-named group cannot have been directly derived from them. The suspensorium, as well as the very massive palatoquadrate bar, fuses with the skull, and, as in Amia calva (a J'/llJO Va A: ':> • W« FIG. 53.—SKULL OF Polypterus bichir FROM THE DORSAL SIDE. Pmx, premaxilla ; Na, external nostril; N, nasal ; Sb, Sbl, anterior and posterior suborbital; Orb, orbit ; M, m
Elements of the comparative anatomy Elements of the comparative anatomy of vertebrates elementsofcompar00wied Year: 1886 THE SKULL. In other points, however, they differ considerably from all these ; and it is clear that the last-named group cannot have been directly derived from them. The suspensorium, as well as the very massive palatoquadrate bar, fuses with the skull, and, as in Amia calva (a J'/llJO Va A: ':> • W« FIG. 53.—SKULL OF Polypterus bichir FROM THE DORSAL SIDE. Pmx, premaxilla ; Na, external nostril; N, nasal ; Sb, Sbl, anterior and posterior suborbital; Orb, orbit ; M, maxilla; Sp, spiracular bones; PO, preoperculum ('(); SO, suboperculum ; Op, operculum ; F, frontal ; P, parietal ; a, b, c, d, supra- occipital shields. The two arrows pointing downwards under the spiracular shields show the position of the openings of the spiracles on to the outer surface of the skull. bony Ganoid), even some of the anterior vertebrae with distinct neural arches and transverse processes are united with the occipital region of the cranium (Fig. ~>4>, W, IV1). (Cp. note on p. 56.) Posterior in addition to anterior nasal apertures appear in the Dipnoi for the first time : this is an indication of air-breathing. Cranial bones are not nearly so numerous as in Ganoids, and F 2
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