396 PROF. T. JEFFEEY PAEKEE ON THE CRANIAL OSTEOLOGY, 



posterior surface of the bone at a slightly lower level than the mesial one, and in one 

 specimen of Dinornis rohustns there are two additional foramina on the posterior 

 surface, one at the level of the mesial aperture, the other close to the head. On the 

 whole the characters of the quadrate appear to be too variable to be of much use for 



systematic purposes. 



The orbital process is laterally compressed and bluntly pointed. On its mesio-ventral 

 border is a small facet [pterapophysial facet, Owen) for the pterygoid, and at the base 

 of the same border and extending downwards on to the body of the bone is a larger 

 facet with which the posterior end of the pterygoid articulates. 



The ventral face of the body bears the usual two condyles for articulation with the 

 mandible. The inner condyle is placed transversely and is separated by a narrow 

 interspace from the outer condyle, which is set at an angle of about 45° with the sagittal 

 plane. Immediately above the outer extremity of the external condyle is the deep 

 hemispherical fossa for articulation with the quadrato-jugal. 



f. The Mandible. 

 The lower jaw consists of two gently curved rami ankylosed with one another in front 



in a wide symphysis. 



Each ramus is expanded at its posterior end to form a cup-like articular surface for 

 the quadrate, the outer border of which projects but slightly beyond the level of the 

 ramus, while internally it is much produced and ends in a triangular internal angular 

 process. The surface for the outer condyle of the quadrate forms a long narrow facet 

 runnino- parallel with the outer and posterior edge of the cup : that for the inner 

 condyle is an oval surface, deeply concave from within outwards, situated on the anterior 

 margin of the cup, just mesiad of its junction with the ramus. At the base of the inner 

 surface of the internal angular process is a nearly circular pneumatic foramen, which, 

 however is sometimes absent in Emeus and Mesopteryx. At the posterior end of the 

 surface for the outer condyle the bone is produced iwto 2i posterior angular process, 

 which is small in Dinornis, large and prominent in the other genera. Both internal and 

 posterior angular processes are continued on to the ventral surface of the articular cup 

 by ridges which meet each other below : they are especially prominent in Emeus. 



The ventral edo-e of each ramus has a sigmoid curve in all genera but Anomalopteryx, 

 beino- convex downwards in its posterior, concave in its anterior half, and the latter 

 beino- more or less deflected. The curvature of the dorsal follows to some extent that 

 of the ventral border, but is less regular. The deflection is most marked in Dinornis, in 

 which, when the mandible is placed upside down on a horizontal surface, the tip of the 

 beak is raised 35-45 mm. above the horizontal. In Pachyornis, Mesopteryx, and Emeus 

 this distance does not exceed 10-15 mm., and in Anomalopteryx the jaw is nearly 

 strai"-ht. The o-eneral plane of the ramus is vertical or nearly so in Fachyornis, 



