1901.] EEPTILES EUOM 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 : — Margiual 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 \^ith nasals, 

 which are long and narrow, tapering forwards. Vertebra? with 

 low, delicate neural spines. 



The type species, of wliich remains are now described, may be 

 named D. jjatagonica, and defined by the minor characters of the 

 head-bones already noted. 



III. Jaws of a Cabnivorous Dinosaue, Genyodectes sesus, 

 gen. et sp. nov. (Plates XYIII. & XIX.) 



Interesting evidence of an unknown large carnivorous Dinosaur 

 is furnished by the fragmentary jaws of one individual obtained 

 by Mr. Eoth from red sandstone in the Caiiadon Grande, Chubut. 

 The bones and teeth are friable and much fractured, but the speci- 

 men comprises the premaxillse, 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, 

 wdth 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 XIX. 

 fig. 1), while a front view of the premaxillse is given in another 

 (Plate XVIII. fig. 3). 



The premaxillee {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. AH these teeth are much broken ; but it is 



