ON THE SKULL OF NYCTODACTYLUS 525 



sphere, smoothly rounded, and with a small pit in its center. It 

 seems to have looked downward and backward at an angle of 

 about 45 , though it is possible that its angle with the horizontal 

 plane of the skull may have been slightly greater. The basi- 

 occipital forms a rounded, somewhat concave and roughened 

 surface, clearly directed at a considerable angle backward. The 

 paroccipital process is a broad, flattened bar, directed outward, 

 backward, and somewhat upward to join the squamosal and 

 quadrate broadly. Above them there is a small vacuity, as 

 already described, while the outer extremity expands to join 

 closely the inferior posterior surface of the quadrate, reaching 

 nearly as far as their middle. The supraoccipital is directed 

 upward and backward, joining the parietal in forming the pos- 

 terior flattened prolongation of the skull. Their separation can- 

 not be made out, but the two together form a considerable 

 concavity looking downward and backward, with a slender 

 median crest — the occipital crest — along the outer two-thirds. 



The quadrate is more narrow above, and is firmly united with 

 the opisthotic, squamosal, and " quadrato-jugal " above ; below 

 and to the outer side with the jugal ; internally below with the 

 pterygoid. The articular surface looks more nearly downward. 

 The transverse axes of the two join each other at an angle of 

 about 20°. Each has a deep oblique trochlear groove running 

 from within outward and backward, with the stronger convexity 

 at the inner extremity. The basi-sphenoid is an elongated, 

 flattened, or slightly convex bone, somewhat wider in front 

 than behind, with concave sides, and situated in the same plane 

 with the pterygoids and palate. It joins the pterygoids at 

 each anterior angle broadly and flatly. 



The pterygoid is firmly and indistinguishably united with 

 the quadrate at its lower inner extremity, close to the articular 

 surface, by a broad process which ascends slightly to the plane 

 of the palate. The two bones are separated from each other 

 throughout their entire length, or at most touch each other by 

 the slender tips of the anterior inner processes. Anteriorly 

 the bone divides into two unequal processes — a slender one, 



