A treatise on zoology . ner-ally thin, cycloid, sculptured, and without cosmine. A shiny cosndnelayer is, however, preserved in Gyroptychius, in which genus the scalesare somewhat rhomboid. The caudal fin is diphycercal or hetero-diphycercal {Trisiichopterus). Usually there are three well-marked lobes,into the middle one of which projects the extremity of the notochord(Figs. 253 and 258). The paired tins are obtusely lobate, and not strictlymesorachic ; the fin-lobe is somewhat triangular and the anterior edge isstrengthened (p. 282). There is in some a small median anterior gularplate, and th
A treatise on zoology . ner-ally thin, cycloid, sculptured, and without cosmine. A shiny cosndnelayer is, however, preserved in Gyroptychius, in which genus the scalesare somewhat rhomboid. The caudal fin is diphycercal or hetero-diphycercal {Trisiichopterus). Usually there are three well-marked lobes,into the middle one of which projects the extremity of the notochord(Figs. 253 and 258). The paired tins are obtusely lobate, and not strictlymesorachic ; the fin-lobe is somewhat triangular and the anterior edge isstrengthened (p. 282). There is in some a small median anterior gularplate, and the teeth are considerably folded at their base. The endo-skeleton is generally well ossified, bony, ring-like centra being frequentlypresent [488, 445, 450]. It is evident from the structure of the paired fins that the Rhizodontsdifter considerably from the previous three families, and they shouldperhaps not be included in the same Order (Figs. 244, 252). Gyrojifychius, IMCoy ; Tridi chapter us, Eg. (Fig. 253); Devonian,. Fio. Tail oiDiplopterus Agussigii, Traill. (AfterTraciuair.) , extremity of axis ; , anallin ; cf, liypochordal fin ; </./, dorsal fin. Carboniferous and 286 OSTEOL EPID O Tl Scotland. )tcrus, Hall
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