MARYLAND GEOLOGICAL SURVEY 37 



temporal fossae approach together on the median line, forming a short 

 sagittal crest, which is about as wide as it is long. From this the tem- 

 poral ridges diverge abruptly, and these extend in a nearly straight line 

 forwards, diverging from the line of the axis of the skull at an angle 

 of about twenty-five degrees. Between it and the lateral occipital crest 

 the temporal fossa is concave to the line of the anterior border of the 

 squamosal bone. At the latter point the line of the suture presents 

 an angle, which extends downwards, outwards and forwards. Between 

 it and the posterior temporal crest the surface is concave above. 



" The exoccipital is flat vertically, and extends a little posterior to the 

 transverse line of the occipital condyles. The postglenoid face of the 

 squamosal is vertical, and it projects laterally beyond the exoccipital. 

 The postglenoid crest is not conspicuous, and the glenoid cavity pre- 

 sents downwards, and very little forwards. The posterior temporal 

 crest bounds a groove of the superior face of the part of the squamosal 

 that lies posterior to it. The latter face is quite wide, and its external 

 bounding angle is a right angle. It is continued as the superior face 

 of the zygomatic process. 



" The petrous bone has a peculiar form. Its mastoid portion presents 

 externally a nearly discoid outline between the exoccipital and squamo- 

 sal. Its inferior portion descends as a process which forms the short 

 stem of a half-tubular horizontal portion, which opens downwards and 

 posteriorly, forming a partial meatus auditorius. 



" The lateral descending borders of the basioccipital are so prominent 

 as to enclose a deep groove between them. The posterior nares are 

 about opposite to the anterior border of the foramen lacerum. 



" The frontal region at its posterior apex is convex from side to side. As 

 it widens it presents three subequal faces, two lateral and one median. 

 The median plane is separated from the laterals by a shallow groove 

 on each side, which become deeper anteriorly, and turn abruptly out- 

 wards at the narial border. They appear to be the outlines of the nasal 

 bones. Anteriorly the lateral planes become thickened longitudinally 

 just external to these grooves. The entire anterior portion of the 

 external planes is a sutural surface, with longitudinal grooves for a 

 length averaging 40 mm. This surface can relate to nothing but the 



