comparative: oology of north American birds. 



Bv R. \V. Snri.Ei.DT, SI. 1). 



The only object of this paper is to bring together what is already 

 well known in regard to the oology of North American birds, placing 

 it before the ornithologist in a more condensed form than it is usually 

 given and in a comparative way. The question of the variation in 

 the matter of form and coloration of the eggs of the birds of this and 

 other countries has interested the writer for many years, and in the 

 light of our present knowledge of the relations existing between birds 

 and reptiles, both in this age and the past ages of the world, I have 

 often wondered at what the causes were that eventually brought 

 about the variation in color and form of which I have just spoken. 



So far as the writer is concerned, he is not aware of the discovery of 

 the eggs of any of the now extinct forms of reptiles, either fossil or 

 subfossil, and it is beyond all probability that we will ever know what 

 the eggs of Archceopteryx, or any of the toothed birds of the Kansas 

 Cretaceous beds (Hesperomis, Ichthyomis, and others), or, indeed, any 

 of the smaller extinct types of Aves, looked like. We have in our 

 possession but very little upon this subject. Of the extinct Dinornis 

 of New Zealand, and of the ponderous JEpyomis of Madagascar, also 

 extinct, we have their eggs in a subfossil state, but except in the point 

 of size they probably did not markedly depart from those of existing 

 Ostrich types of birds (Struthionidce) now living and most nearly 

 related to them. 



All of the eggs of the common African Ostrich (Struihio camelus) that 

 1 have examined have been of a more or less ellipsoidal form, unitinted, 

 and with hard, flinty, and externally polished shells.* Their peculiar 

 mode of incubation is well known and has been faithfully described by 

 Lichenstein.t During the breeding season a cock Ostrich associates 



"North African Ostriches, strange to say, differ remarkably from those of the Cape 

 of Good Hope birds, in so far as the eggs of the former have a perfectly smooth, 

 ivory-like surface, while those of the latter are rough-surfaced and dinted all over 

 with minute punctures; yet no specific difference seems to obtain between the forms 

 of the birds themselves from the two localities mentioned. 



t Lichensteiu, SI. II. K. : Reise im siidlichen Africa, II, pp. 42-4."> ( Berlin, 1812). 



461 



