24 THE ROYAL SOCIETY OF CANADA 



The specimen to be now described, Cat. No. 138, plates I and II, 

 belonging to the field collection of 1913, includes most of the upper 

 back part of the skull as far forward as the fronto-nasal suture. The 

 occipital border is preserved, and the lateral borders forward to the 

 orbits, supplying the full breadth of the head behind. Whereas the 

 original specimens, and a number of those collected at later dates, 

 consist mainly of the coalesced parietal and frontal bones, the present 

 specimen includes elements in place external to the parieto-frontal 

 mass. 



As seen from above, the specimen in outline ends squarely be- 

 hind, and runs forward with a very slight diminution in breadth to 

 the middle of the orbital rim, the postero-lateral angles being rounded. 

 The upper surface is broadly elevated medially in the anterior two- 

 thirds of its length, the elevation having the form of a nearly hemi- 

 spherical boss which anteriorly is extended narrowly forward with an 

 even downward slope in the longitudinal midline. The remainder of 

 the upper surface slopes away from the base of the elevation in a 

 broad posterior area and comparatively narrow lateral ones, the whole 

 surface, apart from the central swelling, being decidedly convex 

 transversely and more moderately so in a longitudinal direction. 

 The elevation has numerous surface pits which are connected to- 

 gether by linear depressions which mark the sides of the columns 

 forming the dense thickening of the cranial elements, the pits occurring 

 at the angles of the columns. On the outer ends of the columns them- 

 selves are much smaller depressions, variable in number and shape but 

 mostly rounded in outline. These pits, of both sizes, are the surface 

 openings of vertical canals in the thick dermal accretion. Round the 

 base of the elevation and over the posterior and lateral areas the bone 

 assumes a warty or lumpy appearance with minor irregular grooves 

 and pit markings, and with the columnar structure less in evidence 

 at the surface. This rugose sculpture, somewhat modified, is con- 

 tinued down on the thickness of the posterior and lateral borders. 

 Midway between the elevation and the posterior border are small 

 supratemporal fossae slightly nearer the midline than the lateral 

 border. Distinct sutures also appear on the upper surface to which 

 reference will be made later. 



Inferiorly in the specimen are the upper and side surfaces of the 

 brain-cavity, antero-laterally the roof of the orbital cavities, and 

 behind them the arch of the infratemporal fossae. The brain-cavity 

 is preserved back to near the foramen magnum but the actual upper 

 curved surface of that opening is apparently not present. Between 

 the posterior end of the brain-case and the infratemporal fossa on 



