546 



PROCEEDmOR OF THE NA TTONA L MUSEUM. vol. xxvr. 



Owing to the crushed condition of the smallei" bones and presence 

 of nunieroas fragnients of other parts associated with the cranium, it 

 has proved luipossibk*, to ascertain the exact ai'i'angenient of th(^ j)alatal 

 bones, although it is apparent that this was (juite diti'erent from that 

 found among existing ])irds, either the Droma'ognatha> or Eurhipi- 

 dur;B. While the head of the quadrate is undivided, the body of the 



P/J 



Pi(j. 1. — Internal anl) kxternal aspect of left quadrate of Hesperornig gracilis, x 1|. 



bone is slender and not overlapped and held in by a descending process 

 of the squamosal; and these are important characters, especially the 

 latter. The short, heavy quadrate of the Dronuvognathw, locked in 

 by the squamosal so as to be practically immovable, is a decidedly 

 reptilian feature, eminently characteristic of the group and widely at 

 variance with the conditions found in Hesperornis. The ascending or 

 lachrymal process of IIesper<>rn!s {fracilis is ver}' long, quite unlike 



that of Hespei'wnis r eg alls as 

 described and figured by Pro- 

 fessor Marsh/' Just at its 

 junction with the body of the 

 quadrate there is a very evident 

 articulation for the pterygoid. 

 The pterygoid has much the 

 same general shape as that of 

 llexijMrornls regalh^ but differs 

 from it slightly in details. It 

 is a small, flat bone, roughly 

 rhomboidal in outline and with three articular surfaces, for the quad- 

 rate, basisphenoid, and palatine, as indicated on the accompanying 

 figures. The most important of these is an elliptical facet at right 

 angles to tlie l)ody of the bone, for this is considered to be the 

 facet for articulation with the ])asisphenoid, and this is connected with 

 the ([uestion of the presence or absence of basipterygoid processes. 

 The entire under surface of the skull is considerably cracked and com- 



«Dr. Beecher, who has kindly examined the Yale specimen, the original of Pro- 

 fe^isor INIarnli's figdre, writes me tliat the process was naturally short and not the. 

 result of any breakage of the superior margin. 



Pig. 2.— Superior and inferior views op right 

 PTERYGOID OK Hespcroriiis gracilis, x I5. jil, Artic- 

 ulation OK palatine; rj, articulation of quad- 

 rate; s, articulation ok sphenoid. 



