522 S. IV. WILLIS TON 



out and smooth ; On the sides between this bone and the roof 

 the space was more or less filled in with a loose cancellated bone, 

 but under the convexity of the middle there was a considerable 

 cavity. On the under side of the premaxillary, back of the anterior 

 ends of the nasals, are two pits or depressions, separated by a low 

 ridge, evidently rhinencephalic fossae. 



The frontal bone is broad, unpaired, smooth, and nearly flat. 

 Anteriorly it extends forward on either side as far as the posterior 

 end of the nares, receiving between its two pointed processes the 

 posterior pointed extremity of the premaxillary, as already 

 described. There is no indication whatever of a median crest, a 

 fact to which doubtless is due the position of the skull upon its 

 dorsal surface, a position which I have never observed in speci- 

 mens of Oniitlw stoma. Plieninger speaks of a rudimentary 

 frontal crest in Pterodactylus, and its entire absence in this genus 

 is remarkable. Posteriorly, the union with the parietal is inde- 

 terminable. On the sides it forms the horizontal, thin, superior 

 border of the orbit for a little more than its posterior half, 

 terminating in an angle a little before the beginning of the 

 attachment of the postfrontal. At the anterior angle the border 

 turns inward with a concavity looking forward, and then curves 

 forward to be continuous with the sides of the premaxillary. 

 The parietal, or fronto-parietal, continues the plane of the frontal 

 in a long, U-shaped plane, forming the rounded posterior extremity 

 of the skull. The sides of this slender U form the inner and 

 front margin of the supratemporal fossa ; from this slightly 

 convex margin posteriorly the parietal descends downward and 

 outward in a thin wing, articulating at the extremity with the 

 posterior flattened end of the squamosal. This wing-like process 

 narrows anteriorly to be continuous with the sides of the brain- 

 case. 



The nasal is a slender bar of bone, beginning on the under 

 side of the premaxillary, a little back of the middle of the nares, 

 and extending downward and outward to unite with the ascend- 

 ing process of the maxilla to form the posterior boundary of the 

 nares. Posteriorly it is a cribriform plate filling up the concave 



