8 R.W. Shufeldt 



It is left to the reader to judge of the correctness of such determina- 

 tions as he did make, and of such species as he described, after a study 

 and examination of the present contribution, including the plates and 

 figures. 



CRETACEOUS BIRDS. 



FAMILY APATORNITHIDAE. 



Genus Apatornis Marsh, 



Marsh, Amer. Journ. Sci., ser. 3, V, 1873, 162. Type, by monotypy, Ichthyornis 

 celer Marsh. 



Apatornis celer (Marsh). 



Ichthyornis celer Marsh, Amer. Journ. Sci., ser. 3, V, 1873, 74. 

 Holotype. Cat. No. 1451, Peabody Museum, Yale University. Butte Creek, 

 Kansas. Upper Cretaceous (Niobrara). O. C. Marsh, collector. 



Fossil sacrum (without the pelvic bones) of a bird about the size of 

 a medium-sized Tern {Sterna), and a thin sliver of fossil bone about a 

 centimeter long and a millimeter in width. 



Marsh first described this specimen as a sacrum of an Ichthyornis 

 {I. celer, antea), but he subseciuently made a new Family and genus 

 for it, i. e. Apatornis. The specimen is very imperfect, and so much 

 compressed for its anterior half, transversely, that the spinal canal 

 has been entirely obliterated. This has given the bone in that locality 

 the very narrow appearance, which, added to the fact that the ventral 

 part has been chipped off on both sides for the entire length, led Marsh 

 to believe that the sacrum was decidedly narrower and morphologi- 

 cally different from the bone as he found it in Ichthyornis. This 

 specimen, palasontologically speaking, is not a kind upon which to 

 base a new genus of extinct birds; and I am of the opinion that the 

 bone in question belonged, in life, to a species of Ichthyornis, and that 

 Professor Marsh was nearer the truth when he described it as Ichthy- 

 ornis celer. Evidently it was in two pieces at one time (it is now 

 glued together at the middle); and it is a significant fact that the 

 hinder half or piece does not exhibit the transverse compression that 

 the anterior half so markedly presents. Indeed, the last vertebra of 

 this sacrum has its neural canal intact, the neural canal not being 

 distorted in any way, while the first vertebra is so much compressed 

 from side to side, that not only is the neural canal entirely obliterated, 

 but the bone itself has lost all semblance to a bird's vertebra in that 

 part of the spinal column. 



