1898.] NATURAL SCIENCES OF PHILADELPHIA. 495 



Bearing this in mind, and from osteological premises, let us now 

 proceed to examine into the probable affinities of certain birds or 

 groups of birds and how we should classify them. An inquiry of 

 this kind would hardly seem to require any apology, in as much as 

 no two systematists of all those who have published a scheme of 

 classification for Aves, since 1867 when Professor Huxley gave us 

 his, agree upon the position in the system and the affinities of not 

 a few of the natural avian assemblages. Take for example the 

 Grebes and Loons. Huxley associated them with the Laridse, Pro- 

 cellariidse, and Alcidse in his Group Cecomorphse ; Garrod placed 

 them among the Ducks and Penguins, in the Anseres; Forbes in- 

 cluded the Heliornitidse with them, and created a new group Ere- 

 topodes ; Dr. Sclater retained them as a family Colymbida? with the 

 Alcida? in the order Pygopodes ; Reichenow did the same, but added 

 the Penguins to the group, and called the order Urinatores ; they 

 are a family of a superfamily, and associated with four other super- 

 families, of the Cecomorphse in Dr. Stejneger's scheme; Dr. Fur- 

 bringer giving still other new names for orders, suborders and genera, 

 places them between the Flamingoes and the extinct Hesperornith- 

 idse ; we find them among the Galliformes in Seebohm's arrange- 

 ment ; and finally considered as two separate orders by Dr. Sharpe. 

 Still other eminent taxonomers, as Cope, Professors Gadow and New- 

 ton, take different views of the subject. In 1890 Professor D'Arcy 

 W. Thompson and the present writer pointed out quite independ- 

 ently of each other the fact that the Loons and Grebes were descend- 

 ants of the Hesperornithidce, an opinion previously expressed by 

 Cope and Fiirbringer. At great variance with this, Professor New- 

 ton, Lydekker, and Marsh, contended that these extinct cretaceous 

 divers were some kind of a natatorial Ostrich. These so-called 

 ostrich or " struthions characters" have been a stumbling-block in 

 times past to more than one avian systematist, but I think their 

 real significance is gradually coming to be better appreciated as 

 time goes on. The great probability is, that there was a time in the 

 former history of the Class, possibly at about the age when Hesper- 

 ornis flourished, that all birds exhibited such characters in their 

 skeletons. They are retained now only in a few and widely separ- 

 ated groups or families, as the Kiwis, the Tinamus, Ostriches and 

 some others. 



Now apart from a general and superficial resemblance a typical 

 Loon and a typical Grebe are not, to judge from their osteology, as 



