72 PKOFESSOE OWEN ON THE 



wielding of long, powerful, massive mandibles, serving most probably to enable the bird 

 to subsist on some proportion of animal diet, in addition to such vegetable food as it 

 might gain from the ground. Such indiscriminate feeding doubtless rendered its flesh 

 less palatable than that of the winged Pigeons of the Mauritius to the Dutch navigators 

 of the sixteenth and seventeenth centuries. 



But the affinities of Didus will be more fully and decisively brought out in the com- 

 parison of the, in this respect, more instructive and light-giving parts of the skeleton. 



§ 10. Comparison of the Skeleton. 



The dorsal region of the vertebral column shows, in some birds, a confluence of 

 certain vertebrae : I have observed four to be so welded together by both centrums and 

 neural spines in Phoenicopterus, viz. the second to the fifth dorsal inclusive, leaving the 

 sixth free, which articulates with the first costigerous sacral vertebra. In Platalea 

 three dorsals coalesce in advance of the antepenultimate free vertebra. In the smaller 

 diurnal bu-ds of prey five dorsal vertebrae are usually confluent, leaving one free vertebra 

 for the lateral movements of the trunk between such dorsal " sacrum " and the pelvic one. 

 In Vultures, Plovers, Bustards, Cranes, Psophia, Cariama, Palamedea, the Penguins, and 

 in all flightless land-bii'ds save the Dodo, no such anchylosis takes place. The Colum- 

 lidie are the species m which the dorsal vertebrae, homologous and the same in number 

 with those of Didus, undergo the process of confluence into one mass of bone : they are 

 the three which immediately precede the last (moveable) dorsal vertebra ; and of these 

 the two anterior develope, in Goura and Diduncuhis, hypapophyses closely corresponding 

 in shape and proportion with those in the Dodo. 



The chief difference which Didus offers in the present region of the vertebral column 

 from that of Cohimbidce is in the greater number of the vertebrae or segments which 

 are typicaUy completed by bony haemapophyses articulating wdth pleiu-apophyses and 

 directly with theu- mass of coalesced and expanded haemal spines constituting the ster- 

 num. Of these typical thoracic segments there were five in Didtis (PL XV.) ; Didun- 

 cuhis (ib.) shows four ; Goura three. In both existing genera these segments are suc- 

 ceeded by a single one, anchylosed to the fore part of the sacrum, but with the pleura- 

 pophysis long and moveable, with its haemapophysis terminating in a point before 

 reaching the sternum, and extensively connected with the antecedent haemapophysis or 

 sternal rib : in both genera two dorsal vertebrae in advance of the typically complete one 

 have moveable pleurapophyses terminating freely in a point, with no hsmapophyses 

 other than the costal processes of the sternum may represent. In Goura, which has six 

 paus of moveable or thoracic ribs, the second pair belong to the first of the three anchy- 

 losed dorsal vertebrae : in Diduncuhis, which has seven paii-s of thoracic ribs, the second 

 pair belongs to the free dorsal immediately in advance of the anchylosed mass. Sup- 

 posing Didus to have had one pair of ribs behind, and two pairs in front of those that 

 directly articulate with the sternum, as the vertebra PI. XVII. fig. 7 indicates, it 



