116 ODOXTORNITHES. 



The tail of Hesperomis was clearly of great service in its aquatic life. 

 In the number of vertebras and length, it exceeds nearly all known birds, 

 and it is unique in its widely expanded transverse processes, and in its 

 depressed, horizontal, plough-share bone. This broad horizontal tail 

 reminds one of that of the beaver, and was undoubtedly of great 

 assistance in steering, and in diving. Whether it was, like the beaver's 

 tail, destitute of feathers, or like the tail of Plotus was furnished with long- 

 stiff rectrices, so as to act as a rudder, cannot at present be determined 

 with certainty, although the latter view seems more probable. That 

 Hesperomis was provided with feathers of some kind, we can hardly doubt. 



The surrounding circumstances were evidently very favorable to 

 Hesperomis for a long period. There was apparently during this time an 

 absence of enemies in the air above, and an abundance of food in the 

 water. Hesperomis was more than a match for the gigantic toothless 

 Pterodactyles, which hovered over the waters here in such great numbers, 

 and the other inhabitants of the air all appear to have been small. The 

 ocean in which Hesperomis swam teemed with fishes of many kinds, and 

 thus a great variety of food was at hand, and obtained with little effort. 

 In this aquatic paradise Hesperomis flourished, disturbed only by the 

 serpentine Mosasaur, which, even without tradition, we may imagine, 

 caused its banishment, if not its destruction. 



In the preceding description, the writer has compared Hesperomis with 

 the Ratitse, or Ostrich group, and also with the diving birds as exemplified 

 by Colymhus and Podiceps, and the more noteworthy points of resemblance 

 or difference have been stated. It will hardly be profitable to extend the 

 comparison to other groups of modern birds, as the similarity in points of 

 structure is mainly of a general nature. 



The genus Arclmopteryx from the Jurassic of Europe, the only bird at 

 present known more ancient than Hesperomis, presents some marked points 

 of difference, for example, its elongated tail ; as well as some peculiar resem- 

 blances, which will be discussed in the concluding part of this volume. 



