304 Annals of the Carnegie Museum. 



external surface shows its cancellous structure, and it is only meagrely 

 covered in certain places by irregular areas of very thin compact os- 

 seous tissue. These are generally off-shoots from the external surface 

 of the rami. The superior surfaces of the inturned borders of the den- 

 tary portion do not show this cancellous structure, but are smooth and 

 unmarked, with their inner free edges rather sharp. Viewed upon its 

 inferior aspect, the hinder boundary of this part of the mandible is 

 seen to be concave, with the convexity directed forwards and it is 

 marked by a deep, median, ipiadrilateral notch. Beyond this notch 

 the bone is profoundly and broadly furrowed mesially, for the distance 

 of about three centimeters. A median crest of bone divides this fur- 

 row into two equal longitudinal halves. The excavation dies out 

 within about two centimeters of the surface, marked distinctly by a 

 dozen or more peculiar striae that converge towards the tip of the bill, 

 but fail quite to reach it. Either ramus of this mandible is smooth, 

 and for the most part shows no cancellous structure. Its upper and 

 lower borders are rounded off, especially the superior one. Anteriorly, 

 just before passing into the dentary portion, described above, it is some- 

 what swelled from side to side. On the mesial aspect of the ramus, be- 

 tween this locality and the articular cup, there is found an elongated 

 elliptical concavity, showing some cancellous structure in its anterior 

 portion. The outer surface of either ramus is very smooth and the 

 ramal vacuity is completely obliterated. On this surface, below the 

 coronoid process, a small subcircular foramen is constantly found. 

 From the fairly-well marked coronoid process to the mandibular artic- 

 ulation, the superior ramal border drops abruptly. The " articular 

 cups" present nothing very peculiar ; they have the usual inturned 

 hooked mesial processes, with the pneumatic foramen on the upper 

 side, near the apex. I'he articular concavities and convexities are 

 conformed to meet the opposing articular surfaces offered on the part 

 of the mandibular articulatory process of the quadrate. 



The apophysis at the angle of the jaw is conspicuously developed, 

 and uniformly recurved upwards and backwards. Its lower and hinder 

 margin is dull, and directly continuous with the inferior margin or 

 border of the ramus. The anterior margin is jagged and sharp, while 

 the apex is rather squarely rounded off. As in the anserine fowl, these 

 angular apophysial projections are lamelliform in character, being thin 

 and greatly compressed in the transverse direction. 



In my specimen of Pluviiicoptcrus ruber the sclerotal plates of either 



