Body fusiform, with rhombic ganoid scales. Notochord persistent, with the vertebral arches ossified. Heterocercal. All the fins with fulcra; dorsal short. Branchiostegals numerous, the foremost pair forming broad gulars. Teeth small, conical, or cylindrical.
Extinct. Many genera are known; from the Old Red Sandstone—Chirolepis and Acrolepis; from Carboniferous rocks—Cosmoptychius, Elonichthys, Nematoptychius, Cycloptychius, Microconodus, Gonatodus, Rhadinichthys, Myriolepis, Urosthenes; from the Permian—Rhabdolepis, Palæoniscus, Amblypterus and Pygopterus; from the Lias—Centrolepis, Oxygnathus, Cosmolepis, and Thrissonotus.
[See Traquair, “The Ganoid Fishes of the British Carboniferous Formations.” Part I. Palæoniscidæ.]
Seventh Family—Platysomidæ.
Body generally high, compressed, covered with rhombic ganoid scales arranged in dorso-ventral bands. Notochord persistent, with the vertebral arches ossified. Heterocercal; fins with fulcra; dorsal fin long, occupying the posterior half of the back. Branchiostegals numerous. Teeth tubercular or obtuse.
Extinct. From Carboniferous and Permian formations—Eurynotus, Benedenius, Mesolepis, Eurysomus, Wardichthys, Chirodus (M’Coy), Platysomus.
[See Traquair, “On the Structure and Affinities of the Platysomidæ”, in “Trans. Roy. Soc.,” Edinb., vol. xxix.]
Fig. 147.—Platysomus gibbosus.