ODONTORNITHES 



PA.RT II. 

 ODONTOTORM^E. 



(Plates XXI-XXXIV.) 



m ■» * 



CHAPTER IX. 



THE SKULL AND TEETH OF ICHTHYOSIS. 

 (Plates XXI, XXVI, and XXXIV.) 



Thu: birds included in the second order of Odontornithes, so far as now 

 known, were all of small size, and possessed powerful wings, and very 

 small legs and feet. They differed widely therefore in form and habit 

 from those described in Part I, and, as we shall see, exhibited various 

 significant characters, which distinguish them more strongly from the 

 Odontolcce than any existing birds are separated from each other. Some of 

 these characters, as for instance their biconcave vertebrae, separate them 

 widely from all birds recent and extinct, and point back unmistakably to 

 a very lowly ancestry, even below the reptiles. 



The remains of this group preserved are more or less pneumatic, and 

 this fact, in connection with their small size, is perhaps the main reason why 

 so few have been discovered. As might naturally be expected, the hollow 

 bones of flying birds, being filled with air, enable the carcass to float 

 upon the water much longer than it otherwise would, and it is thus 

 liable to be destroyed by fishes or other animals. Hence, the chances of 

 the entombment of a complete skeleton are greatly diminished. Such 

 delicate bones, moreover, even after their entombment, require a favorable 

 combination of circumstances for their preservation in good condition. 



