Vol.69.] SKELETON" OB" OBKITHODESMCS LATIDENS. 377 



The Bones of the Skull. 



The Premaxillae. 



The premaxilke (PI. XXXVII, fig. 5, p.) comprise the whole of 

 the upper jaw anterior to the nares, and include the whole alveolar 

 tract of each side. Dorsally they are produced backwards as a 

 triangular rod, which is nowhere wider than 15 mm. This bar is 

 prolonged to the frontal, but to what distance they continue to 

 take a share in it is not clear. The premaxillo-maxillar suture is 

 apparently beneath the anterior edge of the nares. 



The Maxilla. 



The maxilla (PI. XXXVII, figs. 2, 4, & 5, m.cc.) is an extremely 

 thin, long, narrow bar of bone, of little depth. There is a slight 

 increase in depth at each end, with the posterior extremity the more 

 expanded. Here the inner dorsal margin is raised above the outer, 

 and on its posterior border it is fused to the jugal. Its exterior 

 surface is concave. Xear the tip of the snout, and below the 

 anterior end of the external nares, the inner ventral margin is 

 produced inwards, as a sheet of bone, and meets a similar process 

 of the maxilla of the opposite side, completely roofing the palate. 

 How far backwards this plate was continued, it is impossible to 

 say, on account of the lost section. The maxilla comprises the 

 inferior boundary of the nasal and antorbital vacuity, and extends 

 to the quadrate, without the intervention of the jugal. The 

 maxilla is edentulous. 



The Nasal. 



The nasal apparently sends down a process to join that of the 

 maxilla, nearly midway between the anterior end of the nasal and 

 the posterior extremity of the antorbital fossa. That this is so 

 seems to be proved by the presence of the maxillar process: for, 

 where the nasal and preorbital opening is confluent, as in Ptero- 

 dctctylus, such a process is not found. The nasals are fused with 

 the backward extension of the premaxillae into a single median 

 ossification. What extent of this dorsal bar they occupy is 

 indeterminable. 



The Lachrymal. 



The lachrymal (PI. XXXVII, fig. 5, Z.) is situated in the upper 

 anterior corner of the orbit. It looks forward into the ant- 

 orbital vacuity. It is triangular, with the apex of the triangle 

 pointed downwards, and bifurcated : the two branches unite with the 

 upper end of the jugal, and form together an elongated foramen. 

 Where it shares in the orbital rim, it is strongly convex, and, 

 between here and the prefrontal, concave. 



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