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Show 170 ON FOSSIL BIRDS FROM MADAGASCAR AND EGYPT. [Jan. 19, channelled by the groove for the extensor tendons (text-fig. 15, A, e.g.) ; this groove is closed at its lower end by a strong ridge running upwards and outwards towards the outer border, and forming a prominent rugose surface above the outer condyle. Thex-e was no bony bridge over the tendons, but a slight ridge along the inner side of the groove mar-ks the insertion of a strong tendinous sling (see text-fig. 15, A, t.). Conxpax-ing this specimen with the tibio-tarsi of the other Ratites, it m a y be said that to some extent it combines tlxe chax-acters of sevex-al of them. Ixx tlxe depth of the extensor groove it approximates to Rhea and JEpyornis. The oblique ridge which blocks the lower end of tlxe groove occurs also in Struthio, though in this case the groove itself is much shallower. In uEpyornis, on the other hand, the ridge is entix-ely absent and tlxe groove runs nearly down to the condyles. The form of tlxe outer condyle and its relations to tlxe post-condylar process are similar to what is seen in Rhea and to some extent in Struthio also. It seems clear that this bird differs widely from tlxe other Ratites, and cei-tainly from any of tlxe Oarinatse, and I px-opose to name it Eremopezus eoccenus. The dimensions of tlxe type specimen ax-e :- cm. Width of distal articular end 4'8 Width of lower end of shaft (at highest point preserved) 3-5 Width from fx-ont to back of the outer condyle 3#5 The occurrence in this region and in beds of Eocene age of a Ratite bird is a matter of considerable interest; but until sufficient remains are found to give a more definite idea of tlxe relationships of this form, it -will be unwise to draw any vex-y wide conclusions. At the same time, it m a y be remarked that the existence of a true Ratite so long ago as tlxe Eocene makes it at least possible that some of the main gx-oups of the Ratita? may have had a common ancestry, and are not tlxe results of separate x-etx-ogressive modifications leading to the loss of flight, with the various correlated changes. In the present case the x-elationship between the Stx-uthiones and the^Epyornithes, referred to by Burckhardt *, is naturally suggested ; and tlxe occurrence of Struthious birds (Struthio and Hypselornis) in the Pliocene of tlxe Siwalik Hills may possibly indicate some remote connection between tlxe px-esent form and the Dromceus-Casuarius group. There is, however, another possibility that must not be lost sight of, axxd that is, that after all Eremopezus may be merely another instance of retrogressive modification leading to loss of flight and increase of bulk in a group of Carinate birds, such as has occurred in the case of the Stereornithes, the Gastornithes, and * " Ueber JEpyornis," Palaxmt. Abhandlungen, N. F., vol. ii. p. 145 (Jena, 1893). |