CHAPTER VII. 



THE LEGS AND FEET OF HESPERORNIS. 

 (Plates XIII-XX.) 



The posterior limbs of Hesperornis regalis present an admirable 

 example of adaptive structure. The means of locomotion were confined 

 entirely to these extremities, and the life of Hesperornis was probably more 

 completely aquatic than that of any known bird. It may fairly be ques- 

 tioned whether it could even be said to walk on land, although some 

 movement on shore was of course a necessity. Considering the posterior 

 limb as a whole, it will be found a nearly perfect piece of machinery for 

 propulsion through the water. Provision was made for a very powerful 

 backward stroke, followed by a quick recovery, with little loss by 

 resistance, a movement quite analogous to the strong stroke of an oar, 

 feathered on its return. 



Among recent birds, we have, in the genus Podiceps, the nearest 

 approach to the legs and feet of Hesperornis, and the osseous structure of 

 these parts is essentially the same throughout in the two genera. The 

 muscular system, also, of this member must have been very similar in 

 both. In many respects, however, the bones of the posterior limbs of 

 Hesperornis present evidences of a more primitive structure than is seen in 

 any recent diving birds. 



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