174 DB. J. VON HA A ST ON A NEW SPECIES OF DINOENIS. 



but the external symphysial prominence well developed. The mandible consists of 

 the same elements as in the larger Dinornithidse. However, while in these latter the 

 keel of each ramus continues to the posterior wall of the articulation for the tympanic 

 bone, in Binornis oweni the keel disappears before the cup is reached, and an almost 

 flat, or very slightly rounded, lower surface is formed below that tympanic articulation. 

 In the ramus of Meio7ioruis didiformis this flattening out on the lower side for the 

 articulation of the tympanic bone exists also in a minor degree. Now if we compare the 

 cranium of Meionornis didiformis with that of Binornis oweni, the curious fact strikes 

 us at once that, notwithstanding Meionornis didiformis is about twice the size of 

 Binornis oweni, its cranium is actually smaller, with all its parts more slender, showing 

 that that species was not nearly such a powerful bird as the little troglodyte. That 

 Meionornis didiformis was a weaker bird is shown in the first instance by the smallness 

 of the temporal fossae, the slender beak and mandible, and the whole structure of the 

 cranium, in which the prosencephalic part stands above the general level of the 

 calvarium. 



Sir Richard Owen has described and figured the cranium of Meionornis casuarinus 

 (pi. Ixviii. p. 278, op. cit.), witli which, except in size, Meionornis didiformis has a 

 great resemblance in all its principal characteristic features. I may here add that that 

 cranium of Meionornis casuarinus is scarcely larger than that of the small Binornis 

 oweni. It is thus evident that the peculiar mode of life which both Binornis parvus 

 and B. oweni had to follow had endowed them with great strength, while the larger 

 species of Meionornis didiformis and M. casuarinus, leading a difi'erent mode of life 

 on the open grass plains of the South Island, and doubtless feeding on difi'erent food, 

 were endowed with less power but greater swiftness. 



Vertebra. 



The vertebral column belonging to the skeleton of Binornis oweni was unfortunately 

 not complete, so that it is impossible to state the exact number of vertebrae; but 

 allowing for two dorsals missing, it appears that there were seven rib-bearing and 

 twenty-one cervical vertebrae, together twenty-eight. Of the cervical a few are also 

 missing. 



Before ofi'ering a description of a few of these vertebrae, I miglit be permitted to 

 observe that the few complete vertebral columns hitherto known, which were obtained 

 lying close together without intermixture with any other specimen, and which I had the 

 privilege of examining, belonged to the larger species, such as Dinornis elephantopus, 

 B. gravis, and B. rheides. They all possessed seven rib-bearing vertebrae not confluent 

 with the sacrum. Each of these vertebrae has a peculiar character of its own that 

 cannot be mistaken, so that it is not difficult, from a number of dorsal vertebrae 

 belonging to different species, to assign to each its proper place in the series. The 

 same is not altogether the case with the cervical vertebrae, of which there are twenty- 



