THE FOSSIL AVIFAUNA OF THE 
423 
upon the posterior borders of those pelves with the same indentation as it now 
occurs in the corresponding species of tlie existing avifauna. 
The writer entertains the idea that not only were ancient Divers, such as 
Hesperornis, or ancient larine types, such as Ichthyornis^ possessed of teeth and a 
permanent posterior separation of the ilia, ischia, and pubic styles, but that the 
ancestors of a good many of our existing groups of birds enjoyed the samecharactei-s 
in their skeletons. That is to say could we trace back by means of fossil remains 
the present day Cormorants, or Anseres, or Accij)itres and Striges, or perhaps even 
representatives of still higher groups, we Avould, sooner or later, meet Avith fonns in 
the lines of their ancestry wherein the skeletal characters named alwve Avould 
obtain. Not that all would have them, but that many might. Some modern 
Ostrich-forms have the individualization of the pehdc lx)nes ])osteriorly, yet they 
have no teeth in their jaws. Still the ancestors of Tinamusm the Emeu may have 
possessed teeth Avhich have been lost in their descendants Avhile the pelvic charac- 
ters were retained. Surely all very early birds lacked a keel to the sternum siKHicr 
or later. Noav Icthyornis is assuredly a very early avian ty})e, biit Iclhyornis 
is a bird, notwithstanding it has teeth and vertebra^ Avith icthyic characters. 
Could we but find the line of fossil ancestral remains of that genus, Ave must 
believe that in the still earlier forims, after they became really mon* avian than 
reptilian, their sterna lacked the carina, a feature it did not attain until featliers 
and flight AAmre possessed, or Avere developed pari passu with them. There an* tho.se 
Avho believe Archcsopteryx had a keelless sternum, and no one doubts tliat 
it was a fair flyer for short distances. We very mnch need more material in tlie 
Avay of fossil birds, both land-birds and Avater-birds, from the geological horizons 
prior to the Cenozoic era. We cannot hope for much more liglit on the subject 
until such material is obtained. 
The study of the material upon Avhich the present memoir is based still 
further establishes the fact that the birds of the later tertiaiw time Aveiv .simply 
the direct ancestors of existing genera and species of birds, from Avhich in the 
majority of instances they, osteologically at least, scarcely departed at all. Dis- 
regarding for the moment those that became extinct during the lMit)ccne or early 
Quaternary, we may say in other Avords, that the remainder arc e.ssi'ntially 
identical Avith the Psychozoic species they represent. As to the extinct fonns. 
Avhat they teach is not alAAmys clear. We may ncA’cr knoAv, for example, the 
reason for a large, powerful Cormorant passing completely oil’ the scene and Ik'coiu- 
ing extinct. It is not at all likely that any of the small and existing ('ormorants 
are its descendants. It is easier to comprehend Avhy a tertiary' Flamingo shoidd 
perish, as its habitat was sloAvly transformed into a desert region, but it Avill 
not throw much light upon the disappearance of a SAvan, the latter no largt>r <»r 
smaller than its congeners upon either hand. In .some cases the descendants 
are larger and more poAverful than their Pliocenic ancestors, and this may aj)ply 
to the Ravens. A small Fidica may have died out in the ordinary struggle 
