NEW FOSSIL BIRD. 



523 



runs upwards and backwards, then turns backwards ; posteriorly 

 it seems to have curved vip in the direction of the posterior end 

 of the coracoid groove ; beneath the strongly develojDed ridge 

 itself and connected with it are several roughened surfaces. The 

 smooth sides of the keel are marked by numerous fine vascular 

 impressions. 



Tiie chief peculiarities of this sternvim, apart from its large 

 size, are (1) the remarkable strength of its articulations with the 

 coracoids and furcula, indicating the possession of an extremely 

 powerful support for the wings ; (2) the presence of a deep fossa 

 on the visceral surface ; (3) the very strongly marked inter- 

 muscular ridges. These characters seem to show that this bird 

 was a powerful flier, and perhaps also a good swimmer and diver. 

 It is undoubtedly generically distinct fi'om any known species, 

 and I have proposed for it the generic name Gigantornis, the 

 specific name being G. eaglesomei, in honour of the discoverer 

 [Abstract P. Z. S. 1916, p. 30 (May 30th)]. 



Text-figure 4. 



VI. 7? 



Sternum of Diomedea exulans, from side, i natural size. 



Lettering as in text-fig. 3. 



The stippled area indicates the portion preserved in the fossil. 



This sternum has been compared with those of many recent 

 birds, and it seems to resemble in some respects those of certain 

 of the Tubinares and Steganopodes. The anterior aspect is much 

 like that of the sternum of Diomedea (text-fig. 4), the form of the 

 spina externa especially being almost the same ; the disposition 

 of the intermuscular ridges on the carina is also very similar. 

 On the other hand, in Diomedea the coracoid grooves are more 

 oblique, and their anterior ends are separated by a shorter 

 interval ; moreover, there is no deep fossa on the dorsal sin'face, 



