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Show 1901.] REPTILES FROM PATAGONIA. 179 Whereas the modern representatives of the family are small and degenerate burrowing snakes, the largest less than a metre in length, the extinct Patagonian snake, judging by the size of its vertebrae, must have attained a length of at least two metres. It had a relatively large head, and probably resembled the modern Boas in habit. This fossil evidently represents a hitherto unknown genus, which may be named Dinilysia and defined thus :-Marginal teeth of moderate size, about 14 or 15 in the maxillary series; palatine teeth relatively minute. Head rather large, the occipito-parietal region constituting half of the skull, with elevated sagittal crest; frontals longer than broad ; small postfrontals present; prefrontals triangular, almost equilateral, only slightly in contact with nasals, which are long and narrow, tapering forwards. Vertebrae with low, delicate neural spines. The type species, of which remains are now described, may be named D. patagonica, and defined by the minor characters of the head-bones already noted. III. JAWS OP A CARNIVOROUS DINOSAUR, GENYODECTES SEKUS, gen. et sp. nov. (Plates XVIII. & XIX.) Interesting evidence of an unknown large carnivorous Dinosaur is furnished by the fragmentary jaws of one individual obtained by M r . Both from red sandstone in the Cahadon Grande, Chubut. The bones and teeth are friable and much fractured, but the specimen comprises the premaxillae, the greater part of the maxillae and dentaries, and most of the teeth in position. The teeth are implanted in the bone in a single series, and all are invested with a rather thin layer of enamel. They are much laterally compressed, with an acute recurved apex, and finely serrated on the anterior and posterior margins. "When they are broken across at the base, a small pulp-cavity is exposed. The specimen is shown, of one-half nat. size, from the right lateral aspect in one drawing (Plate X I X . fig. 1), while a front view of the premaxillae is given in another (Plate XVIII. fig. 3). The premaxillae (pmx.) are slightly displaced at their median symphysis, proving that they were not fused together; but their sutural connection with the maxillae is not observable owing to fracture on the left side and displacement of the bone on the right. Each premaxilla is nearly as long as deep and its posterior upper portion is curved inwards, while antero-superiorly it rises into the slender, laterally compressed internarial bar which would meet the nasals. Its outer face is gently convex, and the snout, though bluntly rounded, must have been very narrow. There are no distinct indications of vascular foramina. The oral border bears four teeth, which are somewhat obliquely set and so crowded that they overlap each other. The foremost tooth is slightly smaller than the others; the second and third are taller and of nearly equal height; the fourth on the right side is shown to be shorter but broader. All these teeth are much broken ; but it is |