6 ODONTORNITHES. 



The Skull. (Plates I-II.) 



The skull of Hesperorhis regalis, Marsh, is long and narrow, the rostral 

 portion forming- about two-thirds of its entire length (Plate I, figure 1). 

 Viewed from above, the outline of the whole skull is wedge-shaped ; and 

 from the side, it presents a similar form, but somewhat more acute. It has 

 a general resemblance to the skull of Colynibus torquatus, Briinnich (figure 

 2, page 9) ; but the brain-case is smaller, and the facial portion more 

 produced. The position and size of the orbits, and of the anterior nasal 

 apertures, are similar ; but the likeness soon ceases, for the type of cranial 

 structure is essentially different in the two genera. 



In its more important characters, the skull of Hesperornis resembles 

 that of the Batitce, or Struthious birds, and we shall find other striking 

 evidences of affinity with this group in various jDortions of the skeleton. 

 The base of the skull shows nearly all the cranial characters which 

 Huxley, in his invaluable memoir on the Classification of Birds, lays down 

 to distinguish the Batitce, 1 namely: 



(1.) The posterior ends of the palatines, and the anterior ends of the 

 pterygoids are very imperfectly, or not at all, articulated witli the 

 basisphenoid rostrum. 



(2.) Strong " basipterygoid " processes, arising from the body of the 

 basisphenoid, and not from the rostrum articulate with facets which are 

 situated nearer the posterior than the anterior ends of the inner edges of 

 the pterygoid bones. 



(3.) The upper, or proximal, articular head of the quadrate bone is 

 not divided into two distinct facets. 



The occipital condyle in Hesperornis is cordate in outline, and its 

 articular face is only moderately convex (Plate II, figure 4.) It is much 

 less rounded than the condyle in the Batitce, and has a longer base. The 

 articulation looks backward, and there is a shallow median groove on the 

 upper half. The foramina in the base of the skull have the same general 

 position as in recent Struthious birds. 



1 Proceedings Zoological Society of London, 1867, p. 418. 



