120 ODONTORXITHES. 



Fortunately, the bottom of the Cretaceous ocean, in which the remains of 

 these birds were embedded, left nothing to be desired in this respect, since 

 in its fine calcareous sediments the most delicate vascular impressions of 

 the bones were often preserved. 



A most careful search in these deposits, as they are now exposed on 

 the Plains east of the Rocky Mountains, conducted by the writer in person, 

 with the aid ot other members of the various expeditions already men- 

 tioned, has resulted in bringing- to light various remains representing no less 

 than seventy-seven different individuals of this group of the Odontornithes. 

 These remains are all in the Yale College Museum, and form the material 

 on which the following descriptions are based. An investigation of these 

 fossils shows that they are included in two well marked genera, Iclitliyornis 

 and Apatornis, the former represented by several species, and the latter by 

 only one. These were all small birds, scarcely larger than a Pigeon. In 

 their powerful wings and small legs and feet, they remind one of the Terns, 

 and, according to present evidence, they were aquatic birds of similar life 

 and habits. 



The Skull. (Plate XXL) 



In Iclitliyornis dispar, the type of the genus Iclitliyornis, and of the 

 order Odontotomies, the skull was very large in proportion to the rest of 

 the skeleton. This disproportion is shown in the restoration on Plate 

 XXVI. The cranial portion of the skull is quite short, but the facial part 

 is much produced. The occipital condyle is very small, and directed 

 backward. Above the condyle, the occipital portion of the skull was 

 nearly vertical. The lateral margin of this surface is bounded by a sharp 

 ridge which separates it from the temporal fossa, and this ridge united 

 with its fellow above was continued forward on the median line, as a 

 sagittal crest, between the temporal fossse. The latter were large and 

 deep, and were separated from the orbit by a moderate post-orbital 

 process. The orbits were very large, and near together. The quadrate 

 is well preserved in one species, and its articular head has only a single 

 facet, as in Hesperornis, and the Batitce. 



