408 Mr. R. Lydekker on 



of the tibia, and on the general absence of a bony extensor 

 bridge in this bone among the Ratitse. When, however, 

 we reflect on the question of their alleged afl&nity to the 

 Anseres it is very difficult to see how this view can be sustained. 

 Thus, in the first place, it is impossible to imagine how such 

 gigantic birds could have been swimmers, the very weight of 

 their bones being probably enough to sink the greater part 

 of their bodies below the surface of the water. And, in the 

 second place, if they were not swimmers it is probable that 

 the resemblance of their tibia to that of the Anseres is an 

 accidental one, seeing that we must almost certainly regard 

 its form in the latter group as connected with the function of 

 swimming. 



Then comes the question why Gastornis should not be re- 

 ferred to the Ratitse, where, from its giant bulk, the prima 

 facie view would refer it. That the presence of the extensor 

 bridge of the tibio-tarsus is no bar to this view is proved by the 

 invariable presence of the same bridge in all the Dinornithidcs. 

 Moreover, that member of the latter family described by Sir 

 R. Owen under the name of Dinomis elephantopus presents 

 an inflection of the lower end of the tibia at least as well 

 marked as in Gastornis. Again, if the tibia of the latter be 

 compared with that of the extinct Australian Dromornis, 

 such a marked resemblance between the two will be 

 observed as to render it almost certain that they are in 

 some way connected, although the extensor bar is absent in 

 the Australian genus. 



It appears, therefore, to the writer that Gastornis should 

 certainly find a place among the Ratitse ; and this leads to the 

 further conclusion that the absence of the extensor bridge in 

 the tibia of all the existing representatives of that division is 

 in all probability an acquired feature, and that Gastornis and 

 the Dinornit hides j)resent the original plan of structure which 

 is also common to the greater number of the Carinatae, the 

 absence of the tibial bridge in that division occurring only in 

 specialized groups like the Owls, Parrots, and Hornbills. It 

 will further be obvious that if this view be sustained it will 

 strongly support the conclusion that the Carinatse and Ratitae 



