THE CRETACEOUS PERIOD. 



183 



almost to the point of extinction. Concurrent with this, and doubt- 

 less its cause, was an extraordinary development of the legs by which 

 they became not only very powerful, but their efficiency as paddles 

 was increased by the bones of the foot being so joined to those of the 

 leg as to turn edgewise in the water when brought forward. Not 

 only this, but, strangely enough, the legs were so joined to the body 

 frame as to stand out nearly at right angles to the latter, like a pair 

 of oars, instead of standing under the body as walking legs universally 



Fig. 415a. — Restoration of the great toothed diver of the Cretaceous, Hesperornis, 

 by Gleeson, based on a skeleton in the U. S. National Museum. (From Lucas' 

 Animals of the Past; by permission of the Publishers, McClure, Phillips & Co.) 



do. 1 Apparently walking as well as flying had been abandoned, and 

 the organism was specialized for swimming and diving only. The head, 

 neck, and body were elongate and admirably shaped for plunging 

 through the water. Favored by the powerful specialized hind limbs, 

 the Hesperornis was doubtless a swift swimmer and an expert diver, 

 and must have been a formidable enemy to the sea life on which it 

 chose to feed. Its jaws were armed with teeth set in a groove in primi- 

 tive saurian fashion, and, like the jaws of snakes, were separable so 

 as to admit large prey. As these strange birds attained a length of 

 six feet in some cases, their victims may have embraced fish and rep- 

 tiles of considerable size. As they have been found in Kansas, Mon- 



1 Lucas, Animals of the Past, 1901, pp. 81-85. 



