THE CRETACEOUS PERIOD 



427 



were strong flyers, like the gulls, while others were wingless 

 (Fig. 449) and spent their time exclusively in the water, 

 where they had become as expert divers 

 and fishers as the modern penguins of 

 Antarctica. 



Crustal disturbances close the period. 

 - Even before the close of the Cretaceous 

 period various occurrences gave a hint of 

 the revolutionary changes which finally 

 brought the period to an end. In Mex- 

 ico, British Columbia, and elsewhere 

 volcanic eruptions took place on a con- 

 siderable scale during the later part of 

 Cretaceous time. At about the same time 

 some portions of Colorado, Wyoming, 

 and doubtless other regions were warped 

 upward. That the resulting highlands suffered rapid erosion 

 is shown by the coarser and more abundant sediments which 

 were deposited around their borders. 



These disturbances mark the beginning of a widespread 



FIG. 448. A Creta- 

 ceous ammonite 

 (Turrilites) with loose 

 spiral form. 



FIG. 449. A toothed diving bird (Hesperornis) of the interior Cretaceous 

 sea. (Painting by Gleeson. By the courtesy of McClure, Phillips and 

 Company.) 



