1901.] REPTILES FROM PATAGONIA, 175 



base of the postero-lateral " horn." The preraaxillo-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 new fossil : and there are 

 indications of a slight pit for the reception of a pointed mandibular 

 beak on the oral face of the premaxillse. In conformity with this 

 arrangement, the mandible is bevelled on its outer face at the 

 oral margin. Pinally, the nasal chamber in M. platyceps is partly 

 divided by a vertical median septum. 



The type skull of the comparatively large Miolania oiveni, from 

 the Pleistocene of Queensland, has been considerably mended and 

 improved since it was described and figured by Owen\ It is now 

 possible to observe most of its distinctive features ; and comparison 

 shows that in nearly all the particulars in M'hich it differs from 

 the new South American fossil, it agrees with 31. plafyceps. 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 disin- 

 tegration in the fossil. The postero-lateral horns are ovoid in 

 transverse section and point directly outwards, not being curved 

 at the apex. They bear the small supplementaiy boss at the base, 

 already mentioned in M. jylati/cejjs ; and 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 ■. 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 bones differ 

 from those of both these species in projecting forwards consider- 

 ably 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 

 ridging 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. Eoulenger has pointed out to 



^ Eeferred to Mcgalania frisca by Owen, Pbil. Trans. 1880, p. 1041, 

 pis. xxxvii., xxxviii. 



'^ Imperfectly shown by Owen, he. cit. 1880, pi. xxxviii. fig. 3. 



