366 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxv. 



process of the bone extended forward outside of the passage against 

 the inner face of the maxilla. 



A comparison of the palate of C eratosaurus with that of Diplod- 

 ocus, as represented by Marsh ° brings to light both differences and 

 resemblances that are interesting. In describing the palate of 

 Diplodocus it will be convenient to regard it as divided into anterior, 

 second, third, and j^osterior fourths. In this genus, as in Ceratosau- 

 rus, the pterygoids extend far forward, to come into contact with the 

 small vomers. Along the midline they are applied to each other 

 backward nearly to a line joining the articular ends of the quadrates 

 at the hinder end of the third quarter of the length. In the lizard 

 Cyclura they diverge about the middle of the length of the skull. 

 In Diplodocus the postero-inferior process of the pterygoid is very 

 short, on account of the forward swing of the quadrate. Thus the 

 basipterygoid processes join the pterygoids but little in front of the 

 articular ends of the quadrates. 



The anterior position of the articular ends of the quadrates has not 

 been acquired at the expense of the posterior processes of the ptery- 

 goids alone. There seems to have occurred in Diplodocus a remark- 

 able shoving forward of structures that in Ceratosaurus lie across the 

 second and third quarters of the length of the base of the skull. On 

 examining Marsh's figure of Diplodocus it will be observed that there 

 are four vacuities lying in a row across the palate in the second quar- 

 ter of the length. The two of these which are nearer the midline are 

 the internal nasal passages; those lying farther outward, right and 

 left, the postpalatine vacuities. In Ceratosaurus, as in Cyclura, the 

 latter are behind the nasal passages, being separated therefrom by the 

 palatine bones. In Diplodocus the postpalatine vacuities seem to have 

 been crowded forward alongside and outside of the nasal openings. 



Each postpalatine vacuity is mostly inclosed by the maxilla and its 

 processes, only a little of its hinder end being inclosed by the palatine 

 and the transverse bone. The hinder end of the nasal passage lies 

 between the forks of the small palatine. The rest of its inner border 

 is formed by the slender vomer, while it is bounded in front and 

 outwardly by processes of the maxilla. 



"Dinosaurs of North America, p. 177, fig. 27. 



