VERTEBRATA: AVES. 



635 



destitute of a central ridge or keel, and the wings are minute 

 and quite rudimentary ; so that Hesperornis^ unlike Ichthyornis, 



Fig. 352. Toothed Birds (pdontornithes) of the Cretaceous rocks of America. , Left 

 lower jaw of Ichthyornis disbar, slightly enlarged ; b, Left lower jaw of Hesperornis 

 regalis, reduced to nearly one-fourth of the natural size ; c, Cervical vertebra of 

 Ichthyornis dispar, front view, twice the natural size ; c', Side view of the same ; d, 

 Tooth of Hesperornis regalis, enlarged to twice the natural size. (After Marsh.) 



must have been wholly deprived of the power of flight, in this 

 respect approaching the existing Penguins. The tail consists 

 of about twelve vertebrae, of which the last three or four are 

 amalgamated to form a flat terminal mass, there being at the 

 same time clear indications that the tail was capable of up and 

 down movement in a vertical plane, this probably fitting it to 

 serve as a swimming-paddle or rudder. The vertebrae of the 

 cervical and dorsal regions are of the ordinary ornithic type. 

 The legs were powerfully constructed, and the feet were 

 adapted to assist the bird in rapid motion through the water. 

 The known remains of Hesperornis regalis prove it to have 

 been a swimming and diving bird, of larger dimensions than 

 any of the aquatic members of the class of Birds with which 

 we are acquainted at the present day. It appears to have 

 stood between five and six feet high, and its inability to fly is 

 fully compensated for by the numerous adaptations of its struc- 

 ture to a watery life. Its teeth prove it to have been carnivor- 

 ous in its habits, and it probably lived upon fishes. 



From the next order, the present is readily distinguished by 

 the fact that the vertebrae, resemble those of recent birds, the ster- 



