48 University of Kansas Geological Survey. 



formed a complete series. The jaws were united in front by 

 cartilage only, permitting considerable mobility, which was 

 doubtless very serviceable in swallowing their prey, which must 

 have consisted of fishes caught by diving. The bones of the 

 body were solid throughout, not hollow, as in almost all living 

 birds. The sternum had no keel, as in the flying birds and 

 those descended from flying birds, but was as in the ostrich. 

 The vertebrae and skeleton, aside from the teeth, were not un- 

 like those of modern birds, and, were the skull yet unknown, 

 would be unhesitatingly referred to the subclass to which the 

 ostrich, cassowary and rhea belong. A specimen now in the 

 University museum, collected by Mr. H. T. Martin recently, is 

 remarkable in showing the scuta of the tarso-metatarsal region, 

 together with the feathers. A photographic reproduction of 

 this part of the specimen is shown in pi. vni. I have sketched 

 in the tarso-rnetatarsal bone, to show its position. Indications 

 of feathers are also seen on the back portion of the head, and 

 everywhere they appear to be more plumulaceous than the or- 

 dinary type of feathers. 



In pi. vi is shown the restoration of Hesperornis regalis, after 

 Marsh, together with figures of the jaws and of the teeth (pi. 

 vn) . It may be added that the birds were of a low degree of 

 intelligence, as proven by the small size of the brain. 



Ichthyornis was as different from Hesperornis as a dove is from 

 an ostrich. While in Hesperornis the wings were rudimentary 

 and the breast-bone without a keel, in Ichthyornis the wings 

 were large and powerful and the keel well developed. All the 

 members of this group were small, none perhaps much larger 

 than a dove. The bones were hollow, as in most recent birds. 

 The jaws had teeth, like those of Hesperornis, and the birds 

 doubtless fed upon fishes or other small animals. The most 

 peculiar character was, however, the structure of the vertebrae. 

 In all recent birds, as also in Hesperornis, the vertebras have a 

 peculiar articulation, which permitted ample flexure in all di- 

 rections. The articulation is what is called reciprocal mo- 

 tion, or the saddle-shaped articulation, found, for instance, to a 

 moderate extent in the vertebras of the human neck. In this 



