Vol. 69*] SKELETON OF OENITHODESMUS LATIDENS. 401' 



The Maxilla. 



In Pterodactylus, liliampliorhynclius, OmitJiostoma, and JVi/cto- 

 saurns, the jugal and quadratojugal intervene between the maxilla 

 and the quadrate, or are situated in front of the articulation of 

 these bones. In Scapliognatlms purdoni botb the jugal and the 

 quadratojugal are some distance in advance of the articular end of 

 the quadrate underlying the centre of the orbit, where the maxilla 

 terminates. The quadratojugal is vertical and triangular, its 

 comparatively-broad base completely shutting out the maxilla from, 

 the quadrate ; but here is to be seen the initial stage of the union 

 of the maxilla with the quadrate, which was finally attained in. 

 Omithodesmus latidevs. 



The Nasal. 



The nasals in 0. latidens have on each exterior border of the- 

 sigmoidal ventral surface an eave-like edge, which is evidently the 

 vestige of a once greater lateral expansion. In /Scaphognathus 

 crassirostris and Dimorplwdon ntacronyx the nasals spread out 

 as a roof over the antorbital fossae. In Scaphognathus purdoni l 

 their extent has been thought uncertain, as the bone has come 

 away from the areas of their position. On a careful examination 

 of the original specimen in the Museum of Practical Geology, 

 Jermyn Street, London, I found that by the grooving and the 

 direction of the striae on the underlying matrix, the plan of the 

 bones could be made out. The areas in question were not only 

 covered by portions of the nasals and prefrontals, but also by the 

 anterior ends of the lachrymals ; and the singular fact of the bone 

 having come away from two such symmetrical areas appears to be 

 accounted for by the outline being determined by the thickening 

 and strengthening of. the bones forming the upper boundary of 

 the orbit, the antorbital fossa, and the dorsal ridge of the beak. The 

 premaxillary bar is seen to be produced to the frontal, separating. 

 the nasals, Where the latter unite with the premasillse a channel 

 occurs. The nasals are comparatively large bones. The prefrontals 

 by rising processes border the orbits and meet apophyses from the 

 frontal, excluding the nasals from the orbits. The main portions 

 of the prefrontals are wedge-shaped, and are produced forwards, 

 terminating between the nasals and tongues sent out by the 

 maxillo-nasal bars, on their union with the nasals. These maxillar 

 processes are united ventrally to the anterior horns of the crescent- 

 shaped lachrymals, which are situated in the upper corner of the- 

 antorbital vacuities, form moieties of the orbital rims, and meet the 

 ascending branches of the jugals with their posterior horns. The- 

 fractured edges, and the markings on the matrix, appear to prove 

 that the frontal does not reach as far as Mr. Newton suggests. 

 He thinks that it separates the prefrontals from the orbits, but it 



1 E. T. Newton, Phil. Trans. Boy. Soc. ser. B, vol. clxxix (1888) p. 505. 



