MACROPOMA MANTELLII. 



37 



tively thin and rounded off, and extends forwards to the level of the 

 prefrontals (PI. VII., fig. 3 ; PI. VIII., fig. 3), where it articulates 

 with the bone, P/., which it underlies. 



The posterior inferior angle is formed by a very stout neck 

 which bears the transversely elongated condyle for articulation 

 with the mandible. This condyle has a subcylindrical pulley- 

 shaped articular surface, somewhat excavated in the middle, like the 

 distal end of a humerus. 



The upper and posterior angle of the bone, M. is likewise 

 formed by a strong neck, which expands above into a broad head, 

 and articulates therebv with the side walls and roof of the skull 

 (PI. VIII., fig. 2). 



The outer and up'per surface of this bone is remarkably smooth 

 and polished. The inner surface, on the contrary, with the excep- 

 tion of a small strip belonging to the posterior part of the quadrate, 

 is evenly covered with minute asperities, which have, for the most 

 part, more the aspect of tubercles of enamel than of teeth. Along 

 the outer edge, however, they become longer, sharper, and more 

 tooth-like. 



In PI. VIII., fig. 3, the anterior end of the left pterygo-suspen- 

 sorial bone is seen to pass to the ventral side of, and become 

 connected with, the bone PL, which is convex from side to side 

 below, and correspondingly concave above. The inner edge of this 

 bone articulates with the prefrontal, and I conceive that it represents 

 the palatine. 



The concave upper surface of the right palatine is well seen in 

 No. 4241 in the British Museum ; and here again the bone is con- 

 nected on the inner side with the prefrontal, and on the outer, with 

 the anterior end of the pterygo-suspensorial. In the specimen re- 

 presented in PI. VIII., fig. 3, there are no teeth upon the oral sur- 

 face of either of these bones ; but I believe tha't such teeth existed, 

 inasmuch as No. 4237 B.M., the head of which is represented in 

 fig. 3, PI. VII., shows, in the interior of the mouth, a convex 

 plate, P/., covered with small teeth. In this specimen and in 

 No. 4252 B.M. (PI. VII., fig. 6) certain sharp, curved, conical teeth, 

 bh, are visible, which certainly belong neither to the maxilla nor to 

 the bone x, and may have been attached to the palatines. 



The MaxillcB (PI. VIL, fig. 6 ; PI. VIII, figs. 2 and 3) are slender 

 bones which lie alongside the outer margin of the pterygo-suspenso- 

 rial bone, and form the edge of the gape. Their lower edges are 

 beset with small curved teeth. Their anterior connexions are not dis- 

 played in any specimen I have seen. Posteriorly, each abuts upon 

 the apex of an elongated triangular postmaxillary " bone which 

 fills up the interval between the suborbitals, opercula, and mandible, 

 and covers the quadrate articulation. 



Each ramus of the mandible is very stout, and is deepest in the 

 middle third of its length (PI. VIL, fig. 6), where its upper margin 

 is nearly straight. Posteriorly, the upper margin diminishes in 

 height rather gradually ; but, anteriorly, it falls rapidly, being as 

 it were excavated towards the symphysis. 



