Yol. 69.] SKELETON OF OBXITHODESMUS LATIDENS. 379 



The Vacuities of the Occiput. 



The post-temporal fossa of the left side is well exhibited. It 

 is quite small, subcircular, and placed far above the foramen 

 magnum near the upper border of the occiput. The foramen 

 magnum is very large. 



The Quadrate. 



The quadrate (PI. XXXVII, figs. 2, 3, & 5, Q.) is extremely long. 

 It articulates with the mandibles as much as 99 mm. in front of 

 the orbit. Its proximal end is remarkably robust, and so the 

 overlying cranium is weak and fragile in comparison. It forms a 

 third of the depth of this part of the skull. Its proximal dorsal 

 half bends inwards under the supra-temporal arcade. Proximally; 

 externally, it is fused with the squamosal process, between which 

 and the paroccipital process it is immovably wedged. It lies under 

 the squamosal, and forms the lowest angle of the posterior end of 

 the skull. In the median region it is much weaker, and mode- 

 rately tbick ; its dorsal half loses the inward curve, and the whole 

 lateral surface looks outwards. This continues to the distal end, 

 where the bone again becomes more powerful, with a stout, convex, 

 ventral border. Dorsally here it is anchylosed to the quadratojugal 

 for 51 mm. ; proximally to this it comprises the lower boundary of 

 the infra-temporal fossa. Prom the interior surface at its distal 

 end a strong bar of bone extends 29 mm. upwards and backwards. 

 The angle thus made with the shaft of the quadrate is occupied by 

 a Wing of thin bone, which has its origin 86 mm. from the articular 

 end. The pterygoid probably united with the inner angle of this 

 wing, as in Scaphognatlms purdoni. The type of Sc. crassirostris is 

 the only specimen that clearly denotes the form of the inner side 

 of the quadrate. It exhibits a corresponding wing, although the 

 distal border is not a straight line, but sigmoid, and the wing is 

 apparently developed to the full extent of the bone. The articula- 

 tion is a plain pulley-joint, above which the quadrate unites with 

 the lower angle of the posterior extremity of the maxilla. 



The Quadratojugal. 



The quadratojugal (PI. XXXVII, figs. 2, 3, & o, Qu.) is a thin 

 moderately-broad bone, rising obliquely from the maxilla to the 

 anterior termination of the squamosal bar, near the hinder border 

 of the orbit. It is anchylosed to the inner side of this bar. Por 

 about a fourth of its length it forms the lower boundary of the 

 orbit, and for the remaining three-fourths that of the infra-orbital 

 vacuity. At its lower end it is fused for 51 mm. with the quadrate 

 and at its extremity with the maxilla. 



