CHAPTER III. 



THE PRESACRAL VERTEBRAE OF HESPERORNIS. 

 (Plates III-V and XX.) 



'In the type specimen of Hesperornis regalis, a number of vertebrae 

 were preserved from various parts of the series, including nearly all of the 

 caudals. Other individuals of this species, since discovered, have furnished 

 all the missing vertebrae, except the atlas. An examination of the occipital 

 condyle and of the anterior parts of the axis leaves little doubt as to the 

 fomi and proportions of the atlas, so that the entire axial skeleton can now 

 be determined with almost absolute certainty. 



The presacral vertebrae of Hesperornis resemble in their more 

 important characters the corresponding vertebrae of existing birds. The 

 articular faces of the centra conform strictly to the modern ornithic type, 

 an interesting fact, as we shall see, when we compare them with the 

 vertebrae of another group of Odontornithes, from the same geological 

 horizon. 



The neck of Hesperornis regalis was long and slender. Including the 

 atlas and axis, thero were seventeen cervical vertebrae ; and twenty-three 

 in all between the skull and sacrum. The last three cervicals have free 

 ribs, and would be called cervico-dorsals by some anatomists, and dorsals 

 by some others. As the eighteenth vertebra is the first united to the 

 sternum by the intervention of a sternal rib, it seems best to regard it as 

 the first dorsal, and this view will be adopted in the present volume. 

 3 17 



