154 ODOXTORXITIIES. 



The ulnar carpal is less perfectly preserved, its surface being too 

 much eroded to be certain of the limits of the articulations. The face for 

 the ulna is, however, easily recognizable, and is comparatively large. 



The Metacarpals. (Plate XXXI.) 



The united metacarpal elements of Ichtlujornis form a short and 

 decidedly robust bone, somewhat resembling that of Sterna, but presenting 

 more points of resemblance to the genus Graculus. It is, however, pro- 

 portionally shorter and stouter than in that genus, and differs considerably 

 in its proximal articular surface, which is plane transversely, and oblique 

 throughout, with only one curvature. It is consequently destitute of the 

 groove ordinarily seen at the ulnar side of this articulation, and the bone 

 presents no trace of the depression in which this groove terminates in the 

 genus Graculus. 



Of the three metacax'pals, the first extends to the end of the proximal 

 one-fourth part of the bone, and is moderately robust, and, proximally, 

 well elevated. Its distal articular surface is oblique to the axis of the 

 bone, looking forward, and toward the palmar surface of the wing. 



The second of the united metacarpals appears to form by far the 

 greater part of the bone, as in most birds, and bears near the proximal 

 end of its palmar surface, a distinct and well elevated tubercle. The distal 

 half of the anconal surface of this bone bears a groove, running obliquely 

 toward the ulnar side of the bone, passing, near its distal termination, 

 close by the side of a distinct tubercle. A similar groove occurs in Sterna. 

 At the distal end, the bone is rather suddenly expanded, and the articular 

 surfaces, by which it is terminated, considerably resemble those of the 

 same part in Graculus. 



The shaft of the outer or third metacarpal is comparatively slender, 

 as in birds generally, and is nearly cylindrical medially. 



The united metacarpals in the genus Apatornis are much more slender 

 than in Iclitliyornis, but the bone is still of moderately robust })roportions, 

 when compared with the same part in modem birds of flight. Its proxi- 



