OF THE UNITED STATES 167 



a, natural transition between " the Gulls and the Penguins ; and 

 to my friend Professor Alfred Newton " it appears questionable 

 whether the Grebes, Podicipedidce, have any real affinity to the 

 two families (ColymMdce and Alcidce) with which they are usually 

 associated, and this is a point deserving of more attention on the 

 part of morphologists than it has hitherto received." 



Within the confines of the United States we find no outlying 

 types in her avifauna to this group Pygopodes, when constituted 

 as I have above suggested no bird-forms about which the mor- 

 phologists have any doubt as to whether they belong to this sub- 

 order or not; and I conceive that such forms, among other avi- 

 fauna, as we find in the genera Heliornis and Podica, are too un- 

 mistakably stamped with ralline characters, according to recent 

 investigators of their anatomy, to ever be associated again with 

 the Grebes, much less with the Loons. 



The present writer is of the opinion that both the Grebes and 

 the Loons are the descendants of a now extinct ancestral stock 

 of birds, from which those remarkable fossil forms of toothed 

 divers of the cretaceous beds of Kansas described by Marsh the 

 Hesperornithidw were an offshoot. If we designate that ancient 

 stock as the Hesperornoidea, I conceive them to have been forms 

 possessing ample powers of flight and swimming in short, pon- 

 derous flying divers with teeth in their jaws. From those birds 

 it is probable that such types as Hesperornis regalis and H. cras- 

 sipes were a branch, in later time, that for some reason or other 

 ceased to resort to flight, lost their wings in consequence, but 

 became divers of enormous power. 



From a consideration of the osteological characters, I consider 

 the Grebes to be an earlier offshoot of the pygopodous stem than 

 the Loons, and more nearly related to Hesperornis than are the 

 latter birds. The morphology of the pelvis and the pelvic limb, as 

 well as certain characters in the skull and trunk skeleton, point 

 in favor of this view, I think. So far as the affinities of the Pygo- 

 podes are concerned with other groups of existing birds, I have 

 shown in other places that they present a number of osteological 

 characters exhibited in common with the Auks and their allies 

 (Alcce) and the Gulls (Longipennes, etc.). More with the first, 

 and more or fewer with the latter groups. 



The following list gives the genera, species, and subspecies of 

 grebes that are now recognized as occurring in various parts of 



"Encyclo. Brit., 9th ed., vol. XVIII, art. " Ornithology," p. 45. 



