1901,] REPTILES EROM PATAGONIA. 171 



Its peculiar contour is evidently due to the fusion of large dermal 

 ossicles with the bones of the cranial roof and cheeks; but all 

 the sutures are obliterated, except on part of the palate. 



The hinder third of the skull, as seen from above (Plate A.V.), 

 is merely an occipital crest (occ.) consisting of two _ antero- 

 posterioriy compressed, almost laminar bosses of bone, which meet 

 for half their depth in the middle line and fuse together. This 

 crest seems to be solid and is firmly anchylosed with the occipital 

 border of the skull, from which it inclines both upwards and 

 backwards. It is attenuated to a sharp edge at its_ upper and 

 lateral margins, which seem to be complete on the right side ot 

 the fossil ; and its upper margin shows a rounded median exca- 

 vation at the meeting of the two elements of which it is composed. 

 On either side an extremely thin lamina of bone connects the 

 basal half of the occipital crest with a bovine-horn-shaped boss (i.) 

 which projects laterally from the cranium just above the hinder 

 part of the quadrate bone. This postero-lateral prominence is 

 well-preserved on each side of the fossil, and its extent equals 

 that of the crest just described. It is triangular m section, its 

 antero-superior face being largest and flattened ; and it exhibits 

 a sRo-ht curvature which causes its acute distal extremity to point 

 botli' backwards and outwards. Immediately in front of the 

 occipital crest there are three bosses completely extending from 

 side to side of the cranial roof. Of these the median or inter- 

 parietal one (II.) is the smaller and ovate in shape, with its 

 long axis antero-posteriorly directed, and its upper face concave 

 in the middle. Of the lateral (or parietal) pair (m.) only that on 

 the rio-ht side is complete. It is trapezoidal in shape, about as 

 broad as long, and gently rises into a slight, blunt prominence 

 near its middle. It extends nearly as far forwards as the orbit 

 (orb), above which the cranial roof is also thickened. I his 

 thickening is separated by a constriction both from the nasal region, 

 which is flattened, and from a small median triangular area in the 

 frontal region, which is occupied by three low bosses— a P^ir (iv.) 

 behind, a median one (Y.) in front, all broader than long. At ttie 

 base of the postero-lateral horn-shaped prominence on each side 

 there is also a well-preserved, small, laterally-directed boss (vi.), 

 which is depressed and is about on the same level as the root ot 



the orbit. . ., i • • i • f 



All the bosses just described are also visible in a side view ot 

 the skull (Plate XVIL), which exhibits a still smaller, antero- 

 posteriorly elongated, rounded boss (yii.) on the cheek immedi- 

 ately in front of the auditorv opening. As show^n on both sides 

 of the fossil, there is no excavation of the cheek-plates between 

 the orbit and the auditory opening, but the line of the alveolar 

 border is continued directly backwards to the quadrate bone. Ihe 

 nasal roof does not extend farther forwards than the premaxilla3, 

 but the lateral margin of the terminal narial opening (na.) is exca- 

 vated by a constriction between the nasal and maxillary bones. 

 This constriction is continued as a groove to the anterior margin 



