WILLISTON: ON THK SKULL OF ORNITHOSTONLA. 1 97 



bones above, but there can be little doubt that they are distinct 

 elements. The more thickened squamosal measures 6 mm. in 

 width at the middle, while the conjoined width of the squamosal 

 and quadratojugal is nearly 20 mm. The infratemporal opening 

 left between these bones above and the quadrate below is 45 mm. 

 in length and 15 mm. in width at the upper part. It is directed 

 downward and forward, its anterior extremity reaching as far for- 

 ward as the middle of the orbit. The supratemporal opening if of 

 considerable size. The crushed condition of the brain capsule 

 renders it difficult to ascertain its width accurately, but its length 

 directly backward from the extremity of the orbital roof is 25 mm. 

 The width of the completely enclosed cranium across the middle of 

 the fossae can not be over 20 mm. The occipital surface ascends very 

 obliquely upward and backward and was evidently somewhat 

 concave from side to side. The hemispherical occipital condyle, 



9 mm. in diameter, looks obliquely downward and backward. The 

 basioccipital is quadrangular in shape, is gently concave and has 

 two pairs of small, pit-like depressions. The suspensorium, of 

 whatever elements it is composed, is broad and flat, passing 

 dire'ctly outwards and apparently somewhat downwards to the head 

 of the quadrate. The quadrates are very long and are directed very 

 obliquely downward and forward. At its upper part the union is 

 very firm with the opisthotic or supratemporal, the squamosal and 

 quadratojugal. The lower extremity is also firmly and broadly 

 fixed with the squamosal. Running inwards and a little back- 

 wards, as well as upwards from the glenoid articulation is a flattened 

 process which evidently is the pterygoid. The glenoid surface has 

 a transverse diameter of 15 mm. and an anteroposterior one of 10 mm. 

 It has an oblique trochlear surface directed from within outwards 

 and backwards. In front of the glenoid articulation there is a 

 slender opening between the narrow palatines and the maxilla. 

 The palatines at the front end of this opening have a width of 



10 mm. The posterior nares have apparently an incomplete 

 division. They measure together about 30 mm. in width and have 

 a length of about 90 mm. Their margins are everwhere thin. 



