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Show 1901.] REPTILES FROM PATAGONIA. 175 base of the postero-lateral " horn." The premaxillo-maxillary border of the palate in M. platyceps is also peculiar in bearing two sharp inner ridges concentric with the acute oral margin, instead of the one blunt ridge present in the n e w fossil: and there are indications of a slight pit for the reception of a pointed mandibular beak on the oral face of the premaxillae. In conformity with this arrangement, the mandible is bevelled on its outer face at the oral margin. Finally, the nasal chamber in M. platyceps is partly divided by a vertical median septum. The type skull of the comparatively large Miolania oweni, from the Pleistocene of Queensland, has been considerably mended and improved since it was described and figured by Owen1 . It is now possible to observe most of its distinctive features ; and comparison shows that in nearly all the particulars in which it differs from the new South American fossil, it agrees with M. platyceps. It is slightly less depressed than the latter, and its dermal bosses are relatively larger. The occipital crest does not occupy more than one quarter of the total length of the upper face of the skull; its two bosses are less antero-posteriorly compressed and less fused together than in the specimen now described ; while they are peculiar in being hollow-possibly, however, by accidental disintegration in the fossil. The postero-lateral horns are ovoid in transverse sectiou and point directly outwards, not being curved at the apex. They bear the small supplementary boss at the base, already mentioned in M. platyceps; aud the interparietal dermal plate is absent, as in the latter species, while the parietal bosses are relatively very large. The bony lamina of the cheek behind the tympanic cavity is well preserved on the right side and evidently consists in large part of two fused dermal bones. The premaxillo-maxillary border of the palate agrees with that of M. platyceps in bearing two sharp inner ridges concentric with the acute oral border; and the premaxillary pit for the symphysial beak of the mandible is especially deep 2. The median bony septum of the nasal chamber is incomplete, and thus intermediate in development between the conditions observed in the species from Lord Howe's Island and Chubut. The nasal boues differ from those of both these species in projecting forwards considerably beyond the premaxillae. It is thus evident that the new South American skull differs very little from that of the two Australian species of Miolania except in the relative development of its main features. It seems to lack one small pair of dermal bosses which are present in the latter. It differs more considerably in the comparatively simple ridoino- of the border of the palate and the absence of a sharply pointed beak at the symphysis of the mandible. The additional boss however, is merely produced by a notching of the base of the postero-lateral "horn"; and Mr. Boulenger has pointed out to 1 Referred to Megalania prisca by Owen, Phil. Trans. 1S80, p. 1041, pis xxxvii., xxxviii. 2 Imperfectly shown by Owen, loc. cit. 1880, pi. xxxviii. fig. 3. |