. 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. 48 MARINE REPTILES OF THE OXFORD CLAY. bone ( 1), the anterior face of which is concave and forms the lower part of the atlantal cup; its upper ends unite in straight sutures with the lower ends of the bases of the atlantal neural arch (), which unite with the centrum of the atlas in a large nearly triangular facet, which looks forwards, upwards, and outwards, and at its upper end extends the whole length of the centru
. 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. 48 MARINE REPTILES OF THE OXFORD CLAY. bone ( 1), the anterior face of which is concave and forms the lower part of the atlantal cup; its upper ends unite in straight sutures with the lower ends of the bases of the atlantal neural arch (), which unite with the centrum of the atlas in a large nearly triangular facet, which looks forwards, upwards, and outwards, and at its upper end extends the whole length of the centrum; the anterior faces of these basal portions of the arch are concave and complete the atlantal cup, forming the upper halves of its lateral borders. The neural surface of the atlas is nearly triangular, the anterior angle being truncated by the upper border of the atlantal cup. The posterior face is gently concave, with central dimple. It is wider than high and its upper (neural) border is nearly straight, while its ventral border is truncated by the large oblique facet for the second ventral wedge-bone ( 2), which has a more extensive union with the atlas than with the axis. The lateral faces of the atlas are convex from above downwards, and gently concave from before backwards; there is no trace Text-fig. '-'â â '-^ wltis - Ml I "M od ~^2- Atlas and axis of Pdmuustes philarclius, from left side. (R. 2438, § nat. size.) , neural arch of atlas ; ax., axis ; , neural arch of axis ; , neural spine ; od., odontoid (centrum of atlas) ; , rib-facets on axis ; 1, 2, first and second subvertebral wedge-bones. of any facet for an atlantal rib. The neural arch of the atlas () consists of two separate halves, between the upper end of which there is a considerable interval. The enlarged ventral portion unites with the centrum as above described, and forms the upper lateral portion of the atlantal cup. The anterior border of the
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectreptile, bookyear1910
