OF THE UNITED STATES 185 



remarkable extinct cretaceous bird Ichthyornis, of which several 

 species have been found. Heretofore the Black skimmer has been 

 very generally considered by ornithologists to be but a sort of 

 a tern with a different kind of a head; but this is by no means 

 the case, for if any one will take the pains to structurally examine 

 an example of this species, he will soon be confronted by the fact 

 that, instead of being but a "modified tern," it is "separated 

 from the other longipennine families by gaps of no mean width. 

 In other words, it is a very distinct family. The skuas and jae- 

 gers stand between the Rynchopidce and the Laridw, and from 

 what has just been said w r e are prepared to learn that they are 

 far more closely allied to the latter than they are to the skimmers. 

 We have already stated above how this gull group is allied to 

 the auks, and upon carrying our investigations still further we 

 can find no objection to Huxley's observation that " the gulls 

 grade insensibly into the Proccllariidce" while, on the other hand, 

 my own studies fully convince me, in so far as their osteology 

 goes, an even closer relation exists between the gulls and the 

 representatives of the great plover group of birds, or the Litni- 

 co1<r. The Procellariidce are generally considered to include such 

 families as the albatrosses, the fulmars, the shearwaters, and the 

 petrels; and of these perhaps the fulmars, in their general ex- 

 ternal appearance, are more gull-like than any of the others 

 mentioned. 



Tracing our Longipennes back into geological times, there can 

 be no question but what we can see at least some of their ances- 

 tors in the genus of toothed birds of the cretaceous beds of Kan- 

 sas the genus Ichthi/orni-s, already mentioned above; and, in tht* 

 various geological horizons existing between those comparatively . 

 early times and the present epoch, many fossil skeletons of gulls 

 and gull-like birds have occurred. Many of these are in the 

 hands of science, both here and abroad. A few years ago the 

 present writer described a large collection of fossil birds from the 

 Equus beds of Oregon (late tertiary, U. S.), belonging to Professor 

 Thomas Condon and our very distinguished paleontologist, the 

 late Professor E. D. Cope, of Philadelphia. In that collection I 

 found the fossil bones of several gulls and terns, which were 

 identical with those of existing species of our present avifauna. 

 Others were extinct, but nevertheless very closely resembled 

 forms now in existence. In short, this material threw but little 

 light upon the question of the line of longipennine ancestry. 



