. Bulletin of the British Museum (Natural History), Geology. 174 PALAEONISCOID FISHES AND THE CHONDROSTEI the dermosphenotic abuts against the apparently single, long, curved infraorbital bone. Behind the infraorbital and below and behind the dermosphenotic are two suborbitals, of which the dorsal is by far the larger. The maxilla is of the normal palaeoniscoid outline, but its anterior prolongation is somewhat short ; it is ornamented with concentric striae of enamel. The pre- opercular is again of the normal palaeoniscoid form and from the inclination of its posterior border the suspensorium
. Bulletin of the British Museum (Natural History), Geology. 174 PALAEONISCOID FISHES AND THE CHONDROSTEI the dermosphenotic abuts against the apparently single, long, curved infraorbital bone. Behind the infraorbital and below and behind the dermosphenotic are two suborbitals, of which the dorsal is by far the larger. The maxilla is of the normal palaeoniscoid outline, but its anterior prolongation is somewhat short ; it is ornamented with concentric striae of enamel. The pre- opercular is again of the normal palaeoniscoid form and from the inclination of its posterior border the suspensorium can be seen to be almost upright. The opercular is large, ovoid in shape and ornamented with sparse longitudinal ridges of enamel. The subopercular is much smaller larger than the succeeding branchio- stegal ray. At least four branchiostegal rays can be seen, but whether or not a gular plate is present could not be determined. As already mentioned by Watson (in Gill 1923) there appears to be a small triangular plate between the top of the pre- opercular and the dermopterotic. The lower jaw. The lower jaw is ornamented with longitudinal striae of enamel, but apart from the mandibular sensory canal with its three lateral tubules running. Fig. 23. Phanerorhynchus armatus Gill. Restoration of whole fish. out obliquely towards the surface of the jaw little could be made out. Whether or not teeth were present could not be determined : if present they must have been very small. The paired fins and their girdles. Of the pectoral girdle, the supracleithrum and cleithrum are ornamented with concentric ridges of enamel which run parallel to the margins, nearer the centre of the bones these ridges give way to tubercles. The supracleithrum and cleithrum are of normal palaeoniscoid proportions and ventrally there is a pair of stout clavicles. Of the pectoral fin, only the base and one fulcral scale are to be seen on the specimen, but probably there were four to eight fin rays.
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