146 MAEINE EEPTILES OF THE OXEOED CLAT. 



seen in the specimen of Geosaurus gracilis figured in the frontispiece. In Meirio- 

 rhynchus these processes vary much in length, in some cases being very short, while, 

 according to Mr. Leeds, in some skulls of M. superciliosum they may extend two-thirds 

 of the length of the nasal opening; they are often broken away and are not always 

 completely shown in the figures. At the sides of the nares the premaxillae form a 

 thickened rounded border, low in the middle but rising anteriorly and forming in 

 the middle line a well-marked prominence. An incisive foramen on the floor of the 

 nasal opening has not been observed. Behind the nasal opening the premaxillae are 

 produced backwards into pointed facial processes which are thrust between the maxillae. 

 These processes may actually meet the anterior angles of the nasals, thus shutting out 

 the maxillae from the median dorsal line, or they may be separated from them by an 

 interval varying in the different species, and to some degree even in the individuals of 

 one species. Beneath the nares the sides of the premaxillae are rounded from above 

 downwards ; ventrally they are nearly flat and meet in the middle line for a short 

 distance anteriorly, behind which they are produced back into pointed palatine pro- 

 cesses underlying the pointed anterior ends of the palatine plates of the maxillae, 

 which are thrust like a wedge between them as far forwards as the level of the interval 

 between the second and third dental alveoli. Each premaxilla bears three alveoli, 

 which are separated from one another by equal intervals ; the anterior tooth is a little 

 smaller than the others. Between the last tooth in the premaxilla and the first in 

 the maxilla there is usually a diastema of considerable length ; this region is a little 

 concave from before backwards, and is crossed towards its hinder end by the maxillo- 

 premaxillary suture. 



The max/lice [mx.) are very large bones forming a great part of the rostrum. They 

 may meet in the middle dorsal line for some distance, or may be excluded from it by the 

 junction of the premaxillae and the nasals. Their greatest length is along the alveolar 

 border, which extends from the premaxillae to the jugal behind. The number and the 

 distance between the dental alveoli vary considerably in the different species ; thus in 

 M. Iceve there are considerably over thirty teeth in each maxilla, the alveoli being set 

 very close together, while, on the other hand, in HI. hrachyrhynclms there are only about 

 eighteen, separated by intervals equal to at least half the diameter of the alveoli them- 

 selves. Anteriorly the palatal plates of the maxillae are thrust wedge-like between the 

 premaxillae. From this anterior angle they meet in a median suture as far back as 

 the anterior angle of the palatines, which are interposed between them, increasing 

 gradually in width from before backwards. The palatal surface of the maxilla imme- 

 diately within the alveolar border is raised into a ridge which forms the outer border 

 of a longitudinal groove which gradually increases in depth from before backwards. 

 Posteriorly the grooves thus formed run into the notches between the median and 

 lateral points of the anterior ends of the palatines. In this region the grooves become 

 narrow and deep, and appear to have foramina opening into their roof. At first they 



