14 



r^irds (p. Ill) makes the statement that the "-rotip known as 



Impcnncs, and we have seen that Brandt eomhined the two 

 under the name of CruuUonsA^yx^ of their essential chfferenee 

 there can now be no doubt, and indeed it is hard to look upon 

 Pvi^opodcs as a natural group, so man>- are the differences between 

 the PodinpaUdce ox (irebes and Colymiud^c' or Divers, thou-h 

 recent morphologists agree to unite them, while the afhnity of 

 the Divers to the Auks seems to be still more uncertain, and 

 there appears to be ground for considering the Akidic to l)e 

 much modified relatives of the Lnridie." 



The discovery of the toothed Hesperornithidae of the middle 

 cretaceous of America has doubtless modified the opinions of 

 systematists regarding the affinities of the Pygopodes. 



I agree then essentialh' with h'lirbringer in confining the 

 famiUes Colymbidae (loons) and Podicipida (grebes) to a group 

 " Colymbo-Podicipites," and closely associating the latter with 

 the families P^naliornithida^ and Hesperornithida; in a Suborder 

 Podicipitiformes. Therefore I can proceed to the consideration 

 of the osteology of the grebes. 



Grebes may have the superior osseous mandible longer than 

 the cranium, or they may have it shorter than that part of the 

 skull. Of the first-mentioned, Colymbns holbaili is a good 

 example, while Podilymbiis podiccps exhibits the latter character- 

 istic. In C. holbivlli the long, straight and acutely-tapering 

 superior osseous mandible is fully one fourth longer than the 

 cranium, and either narial aperture is suboval in outline, being 

 equal in length to the end of the bill which extends beyond its 

 anterior termination. This narial aperture is rather acutely 

 holorhinal posteriorly, and the dentary margins are cultrate for 



' " American ornithologists have lately used this term for the Grebes, to the great 

 disturbance of nomenclature. It is apparently from the ancestors of the Colym- 

 bid.c, before they lost their teeth, that Hesperornis branched off as a degenerate, 

 bulky and flightless form." — A. N. 



