UPON HYPEEODAPEDON GOEDONI. 



681 



into which the mandibular teeth are received. The palatal and 

 maxillary teeth of opposite sides are separated by the widest part of 

 the palatal area, formed by the pterygoid bones in the middle, and 

 the palatals at the sides. The long oval posterior nares are wide 

 and conspicuous, occupying, as they do, the greater part of the space 

 between the anterior end of the palatal series of teeth and the 

 premaxillary rostrum (see fig. 6, p. 683). 



In Hyperodapedon (Plate XXVI. fig. 3) the alveolar edges of the 

 maxillae describe a curve which is strongly convex towards the middle 

 line, and correspondingly concave outwards. Their posterior ends are 

 very far apart, but in the anterior halves of their extent they approach 

 so closely as to leave only a narrow palatal area. At their anterior 

 ends they again slightly diverge. Behind, three longitudinal rows 

 of obtusely conical teeth are set between the groove for the man- 

 dible and the outer margin of the maxilla, but only one of these 

 rows is continued forwards along the anterior half of the length of 

 the maxilla (see fig. 4, p. 683). 



The space included between the mandibular groove and the 

 eurved posterior boundary of so much of the dentigerous area of the 

 palatal bones as is left visible in the specimen by the dislocated 

 mandible is occupied on each side by four rows of obtusely conical 

 teeth, which take a direction roughly parallel with one another and 

 with the series of maxillary teeth. Only one of these series of teeth 

 is continued forward alongside of the single part of the series of 

 maxillary teeth. 



The palatal bones are undistinguishably united, either with the 

 pterygoids, or over them, in the anterior narrow part of the palate, 

 which ends in a semilunar margin, concave forward. The space 

 between this and the posterior face of the root of the premaxil- 

 lary beak is, for the most part, filled by a broad plate of bone 

 which represents the vomers. The posterior nares must have been 

 very small ; but, on the left side, between a concave edge of this 

 vomerine plate, on the inner side, the premaxilla, in front, and the 

 maxilla, externally, there is a small aperture, which I take to be the 

 posterior nasal opening (Pkite XX YI. fig. 3,p.n). The articular con- 

 dyles of the quadrate bones are elongated from side to side, and present 

 cylindroidal surfaces. They lie about 25 millim. behind a vertical 

 line drawn from the occiput, when the roof of the skull is horizontal. 



In Sphenodon (see fig. 3, p. 682) the rami of the mandible appear 

 nearly straight in the greater part of their length, both in the lateral 

 and the ventral aspects. In the latter, their anterior ends present a 

 sudden incurvature towards the symphysis, which is not longer than 

 in ordinary Lizards ; and, as in them, the union of the rami is effected 

 by ligament. The contours of the alveolar edges of the rami have 

 an upward concavity, which is so slight as to be hardly perceptible ; 

 and, viewed from above, they form a narrow arch with nearly straight 

 sides. The inner and superior angle of the symphysial end of each 

 ramus is separated by an interspace from its fellow, above the sym- 

 physis. The surface of the ramus at this part is tooth-like in 

 aspect, from the density of the bone of which it is composed. 

 Externally, just where the bent portion of the ramus passes into the 



Q. J. Gr. S. No. 172. 3 a 



