. A descriptive catalogue of the marine reptiles of the Oxford clay. Based on the Leeds Collection in the British Museum (Natural History), London ... Reptiles, Fossil. 12 MAEINE EEPTILES OF THE OXFOED CLAY. bone share in the formation of the antero-ventral portion of the facet, as is also the case in the atlas and axis of Trinacromerum (Dolichorhyncops) figured by Williston *. In Peloneustes the rib-facet is borne on the centrum of the axis alone, the second ventral wedge-bone being much smaller than in Pliosaurus. The posterior face of the centrum of the axis is evenly concave, with a well-m
. A descriptive catalogue of the marine reptiles of the Oxford clay. Based on the Leeds Collection in the British Museum (Natural History), London ... Reptiles, Fossil. 12 MAEINE EEPTILES OF THE OXFOED CLAY. bone share in the formation of the antero-ventral portion of the facet, as is also the case in the atlas and axis of Trinacromerum (Dolichorhyncops) figured by Williston *. In Peloneustes the rib-facet is borne on the centrum of the axis alone, the second ventral wedge-bone being much smaller than in Pliosaurus. The posterior face of the centrum of the axis is evenly concave, with a well-marked pit in the middle. The remaining cervical vertebras (text-fig. 2) are about eighteen in number. Their centra are characterised by their shortness, the length in the mid-ventral line, where they are thickest, being less than half the vertical diameter of their articular faces. Text-fig;. Cervical vertebra of Pliosaurus ferox : A, from front; B, from left side. (E. 3536, | nat. size.) ,, anterior zygapophysis ; , cervical rib ; , neural spine ; , posterior zygapophysis. These are nearly circular in outline, the transverse diameter being a little longer than the vertical; beneath the neural canal the upper border is slightly concave; the surfaces are gently concave, with a median pit of such depth that the anterior and posterior pits can only be separated by a very thin layer of bone, but in no case have they been seen actually to communicate with one another. On the ventral side the articular faces have a well-defined rim or border, which in some cases may form a slight hypapophysial prominence, which looks as if it may be formed by a now com- pletely fused intervertebral wedge-bone. The neural surface is slightly concave from side to side; the facets for union with the pedicles of the neural arch are diamond- * Op. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloratio
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectreptile, bookyear1910
