Catalogue of the fossil fishes in the British Museum (Natural History) .. . l heterocercal; squamation rudimentary or absent, except on the upper caudal lobe Polyodontid^:. Family PAL^EONISCID^E. Trunk elongate or elongate-fusiform ; tail heterocercal; scalesrhombic (rarely in part cycloidal), ganoid. Head-bones well-deve-loped, ganoid ; no median series of cranial roof-bones; teeth slender,conical or styliform ; eye far forwards and snout prominent; man-dibular suspensorium more or less obliquely directed backwards anddownwards. A series of broad branchiostegal rays, the most anteriorpair esp
Catalogue of the fossil fishes in the British Museum (Natural History) .. . l heterocercal; squamation rudimentary or absent, except on the upper caudal lobe Polyodontid^:. Family PAL^EONISCID^E. Trunk elongate or elongate-fusiform ; tail heterocercal; scalesrhombic (rarely in part cycloidal), ganoid. Head-bones well-deve-loped, ganoid ; no median series of cranial roof-bones; teeth slender,conical or styliform ; eye far forwards and snout prominent; man-dibular suspensorium more or less obliquely directed backwards anddownwards. A series of broad branchiostegal rays, the most anteriorpair especially large, with a small median element. Dorsal fin singleand not much extended. This is a somewhat comprehensive family, and it is not unlikely tal; 425 that further researches may lead to its dismemberment. The mostimportant contributions to present knowledge of the typical Palaeozoicgenera have hitherto been made by 11. H. Traquair1 j and the ad-ditional observations recorded in the following pages chiefly resultfrom the study of Mesozoic forms. Fig. Palcsoniscus macropomus, Ag.—Head and pectoral arch, restored in outline, byR. H. Traquair. , anterior frontal; , angular; br, branchiostegal rays; cl, clavicle; d,dentary; e, ethmoid ; /, frontal; , infraclavicle; Lop, suboperculum;mx, maxilla; n, narial opening; op, operculum ; p, parietal; , post-clavicle ; , preoperculutn ; , post-temporal; pmx, premaxilla;, supraclavicle; , circumorbital ring and suborbitals; , supra-temporal ; sq, squamosal. No precise particulars are forthcoming as to the ossifications inthe chondrocranium, but the dermal or membrane-bones of the headare conspicuous and well-known. The cranial roof is provided witha continuous shield, of which a small pair of parietals (fig. 54, p)and the flanking squamosal plates (sq) form the hinder portion, whilea large pair of elongated frontals (/), with or without a separate pairof lateral plates, constitutes the m
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Keywords: ., bookauthorbritishmuseumnaturalh, bookcentury1800, bookdecade1880
