CHAPTER XI. 



SHOULDER-GIRDLE OF ICHTHYORNIS AND APATORXIS. 

 (Plates XXIII, XXIX, and XXXIV.) 



The scapular arch of IcMliyornis, and its near ally Apatornis, conforms 

 strictly to the type seen in living carinate birds. This part of the skeleton 

 gives no hint of the peculiar reptilian features in other portions of the 

 structure, and has none of the Struthious characters noticed in Hcsperornis. 

 There is apparently no part of the entire shoulder girdle of IcMliyornis, 

 or the allied genus, that might not have been used by some existing birds 

 with strong powers of flight. 



The Scapula. (Plates XXIX, and XXXIV.) 



In the Odontotomies, the scapula presents two well marked types. In 

 IcMliyornis (Plate XXIX, figures 9, da, 10-12), the bone is robust near 

 its articular end, where it is moderately, but suddenly, expanded and 

 thickened, much as in Ardea. Here, it presents two confluent articular 

 surfaces. The larger of these forms a part of the glenoid fossa, and the 

 smaller is for articulation with the coracoid. The scapular part of the 

 glenoid fossa is flattened, slightly narrower below than above, and 

 strongly inclined to the plane of the bone. In its largest dimension, it is 

 slightly concave in section, while transversely it is nearly flat, but rounded 

 at the edges. The articular surface for union with the coracoid is nearly 



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