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Show ■232 o n T h e d i n o s a u r c e t i o s a u r u s l e e d s i . [Apr. 18. 1. On Parts of the Skeleton of Cetiosaurus leedsi, a Sauro-podous Dinosaur from the Oxford Clay of Peterborough. By A. S m i t h W o o d w a r d , LL.D., F.R.S., F.Z.S. [Received April 14, 1905.] (Text-figures 39-49.) Cetiosaurus is already the best known of European Sauropodous Dinosaurs, owing to the discovery of associated limb-bones and vertebra? in the Lower Oolite near Oxford*. Much new information concerning its principal characters, however, is now afforded by a large part of a new skeleton disinterred with great skill by Mr. Alfred N. Leeds from the Oxford Clay near Peterborough. This specimen is so well preserved that, since its acquisition by the British Museum, it has been possible to mount the various bones on ironwork in their natural position. An opportunity is thus afforded for comparing Cetiosaurus more satisfactorily than hitherto with the better known Sauropoda of Jurassic age in North America. The new specimen discovered by Mr. Leeds, and numbered R. 3078 in the British Museum Register (text-fig. 39, p. 233), comprises four portions of dorsal vertebra?, some neural spines of the sacrum, four anterior caudal vertebrae, a continuous series of twenty-seven middle caudal vertebrae, many chevron-bones, the right scapulo-coracoid and fore limb (lacking manus), parts of both ilia, and the left hind limb. It evidently belongs to the species which has already been named Cetiosaurus leedsi on the evidence of a pelvis (Brit. Mus. no. R. 1988) from the same geological formation and locality f. To the same species may also be referred four associated anterior caudal vertebra? (Brit. Mus. no. R. 1984) and a portion of the wliip-like end of the tail (Brit. Mus. no. R. 1967). All these* bones have the spongy texture so characteristic of the skeleton of Cetacean mammals, and the vertebral centra are therefore quite different from those of the genus Ornithopsis, to which the species now under consideration was originally assigned. In Ornithopsis the centrum of each vertebra is chambered throughout, and the thin partitions between the small cavities consist of hard, dense bone. Dorsal Vertebrae. Vertebral centra which seem to belong to the front and middle of the dorsal series are about as long as deep, and not laterally compressed though somewhat constricted. The centrum of the * J. Phillips, ‘ Geology of Oxford' (1871), pp. 2 45-294 ; R. Owen, ‘ Monograph on the Fossil Reptilia of the Mesozoic Formations ' (Paheont. Soc., 1875), pp. 27-43. f J. W . Hulke, " Note on some Dinosaurian Remains in the Collection of A . Leeds, Esq., of Eyebury, Northamptonshire," Quart. Journ. Geol. Soc. vol. xliii. (1887) pp. G95-699. H. G. Seeley, " Note on the Pelvis of Ornithopsis," loc. cit. vol. xlv. (1889) pp. 391-396. |