. 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. 14 MAEINE REPTILES OE THE OXFOED CLAY. The caudals (text-fig. 3), which are about 25-30 in number, have the centra rapidly shortening as the series is followed backwards, and the last four or five diminish in size very suddenly, the terminal centrum being a small irregularly-shaped nodule of bone, which, however, seems to have borne a rudimentary neural arch, but, so far as can be made out, neither caudal ribs nor chevrons. In
. 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. 14 MAEINE REPTILES OE THE OXFOED CLAY. The caudals (text-fig. 3), which are about 25-30 in number, have the centra rapidly shortening as the series is followed backwards, and the last four or five diminish in size very suddenly, the terminal centrum being a small irregularly-shaped nodule of bone, which, however, seems to have borne a rudimentary neural arch, but, so far as can be made out, neither caudal ribs nor chevrons. In the anterior caudals the articular surfaces of the centra are nearly circular in outline and are gently concave with a deep median pit. The neural surface () is narrow, particularly in the middle where it is encroached upon by the deeply concave facets for the neural arch ('.). The sides of the centra are concave in a longitudinal direction ; on either side they bear a short prominence () with the summit of which the single-headed caudal rib articulated or fused : the nutritive foramina are situated just beneath these costal prominences. The ventral surface of the centrum is only slightly concave in a longi- tudinal direction ; on its anterior and posterior edges are the semicircular chevron- facets (), the anterior looking downwards and forwards, the posterior, the larger of the two, downwards and Centrum of a caudal vertebra of Pliosaurus , from behind and from the left side. (, i nat. size.) , facet for union with neural arch ; , facets for chevrons ; , floor of neural canal ; , facet for rib. Bibs (text-fig. 4).—So far as has been observed, there is no rib on the atlas ; that on the axis is not well known, but seems to have been single-headed and to have articulated with a large facet borne mainly by the axis and partly by the second intervertebral wedge-bone and the odontoid. This facet shows no trace of division into
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectreptile, bookyear1910
