GIGANTIC BIED PEOM LOWER EOCENE BEDS. 155 



rounded and straighter shaft, the smaller proportionate size of the inner condyle, and 

 the diiferent contour of the latter when seen from the side. 



Among the Rails, the one which seems to approach most nearly to Gastornis is the 

 Ocyclromus australis. In this form, and some others at least of the group, the lower 

 end of the tibio-tarsus turns inwards, and the canal and bridge are towards the inner 

 side ; but the condyles are thick as in the Bustard and Turkey, and the inner one is 

 smaller than the outer; besides this, there is no definite intercondylar depression. 

 The Eails seem to be further removed from Gastornis than are either of the three recent 

 forms noticed above. 



The Bustard [Otis tarda) does not have the lower end of the tibio-tarsus turned 

 inwards, the condyles are thick, and the intercondylar trochlear margin rises high. In 

 all these characters it is unlike Gastornis, and approaches rather to the A])terijx and 

 Dinornis. The tendinal canal and lower aperture of the bridge are towards the inner 

 side. The deep intercondylar depression is the character which at first would seem 

 to ally the Bustard to Gastornis; but the form of this depression appears to me 

 quite unlike Avhat we find in Gastornis, and may merely indicate a similarity of 

 function in two different types of birds. 



The Tinamou [Ehynchotus rufescens) has the canal and bridge-aperture very close to 

 the inner side, and there is a moderately deep intercondylar depression ; but the thick 

 condyles and general form of the lower end of the tibio-tarsus resemble the form of 

 that bone in Otis and Apteryx, and are unlike Gastornis. 



One is naturally led, when comparing these large fossil birds with recent forms, to 

 look at the Ostrich and its allies ; but the recent Ratitee seem further removed from 

 our Eocene fossils, in so far at least as regards the tibio-tarsus, than do some of the 

 Carinatae, the lower end of this bone being unlike that of Gastornis, and, moreover, the 

 ossified supratendinal bridge, which is such a distinctive feature of nearly all carinate 

 birds, is wanting in the living Ratitse, although present in the extinct Dinornis. 



The femur of Gastornis is unlike that of any recent bird with which I am acquainted ; 

 but the femur of Cereojwis seems to show some slight indication of the peculiar obliquity 

 of the superior articular surface, which is so strildng a character of Gastornis. 



The comparison of the Croydon Gastornis-remams with recent birds seems to show 

 that most of the characters of its tibio-tarsus are to be found within the limits of the 

 old group of the Palmipedes, the common domestic Goose and the New-Holland Goose 

 {Cereopsis novce-hollandice) having perhaps the greatest resemblance as to general form. 

 The median position of the tendinal canal and lower opening of the bridge, as well as 

 the absence of a definite intercondylar depression, are doubtless important points in 

 which the Common Goose differs from the fossil ; but we have seen that the New- 

 Holland Goose makes a nearer approach, and the Herring-Gull has the canal and 

 bridge near the inner side, besides presenting a remarkable similarity in the characters 

 of the intercondylar space, although the depression of this region is not so deep as it is 



