114 ODONTORNITIIES. 



During the life-history as thus indicated, Sesperornis would exemplify, 

 in the waters of the Cretaceous period the evolution that has recently 

 taken place in ocean navigation, in the gradual change of the side-wheel 

 steamer into the niodem propeller. 



Another explanation seems on the whole more reasonable, and more 

 in accordance with the known facts. The Strufhious characters, seen in 

 Sesperornis, should probably be regarded as evidence of real affinity, and 

 in this case Sesperornis would be essentially a carnivorous, swimming 

 Ostrich. The diminutive wings and very larg-e posterior extremities would 

 then have been acquired on land, by the same means that have given 

 similar characters to the Matitce, and subsequently have been adapted to an 

 aquatic life. Against this view, the carnivorous character of Sesperornis 

 would be no valid objection. The long neck and peculiar jaws and teeth 

 would be equally effective in seizing- prey on the land, and many of the 

 herbivorous cotemporaries would doiibtless have been easy victims. This 

 would be precisely analogous to what we have among the corresponding- 

 groups in the Dinosaurs. 



There is to-day no evidence that any of the Strufhious birds, or their 

 ancestors, ever possessed the power of flight, although this is generally 

 assumed. The case is even stronger with Sesperornis, as this genus stands 

 much nearer the ancestral type, both in structure and in time. The 

 absence from the sternum of any trace of a keel is alone strong proof 

 against flight ; the peculiar Dinosauroid union of the scapula and coracoid, 

 unlike that of any volant bird or reptile, confirms this ; and other testimony 

 bearing in the same direction is not wanting. 



All Carinate birds, moreover, so far as known, indicate by their 

 embryology that they have passed through the Strufhious, or lower stage ; 

 and some of them, Tinamns, for instance, still retain one or more of its 

 distinctive characters. There are, indeed, various flightless birds, recently 

 extinct, which do not belong to the Ostrich group, but are truly Carinate 

 in all their essential features. The Dodo (Didus), Solitaire (Pezophaps), 

 Cnemiomis, and Notomis are well known examples ; but these all show in 

 their shoulder-girdle unmistakable traces of the lost power of flight. The 



