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Dinornis closely resembled the extinct Dodo {Didus ineptus, Linn.) of 

 the Isles of France and Rodriguez ; and as it could not have greatly sur- 

 passed them in size, it has been proposed to designate it Dinornis didiformis . 



Like the larger species of Dinornis, there is not the slightest trace of 

 the articulation of a fourth or posterior toe in the metatarsal of the 

 Dinornis didiformis ; the generic distinction from Didus and Apteryx 

 being thus distinctly indicated in all the tarso-metatarsal bones of the 

 present collection. 



If the different proportions and configurations of the present small 

 tarso-metatarsal bone justify the conclusion that it belonged to a particular 

 species of Dinornis, by parity of reasoning the same inference must be 

 drawn in regard to the intermediate-sized tarso-metatarsal No. 1574, 

 which is far from repeating the proportions of the largest bone, No. 1567, 

 as the dimensions already given demonstrate. No. 1585 is in fact a more 

 robust bone, in proportion to its length; the anterior longitudinal concavity, 

 commencing below the rough depression, is deeper ; the channel leading 

 to the cleft between the condyles for the outer and middle toes is also 

 relatively narrower and deeper ; the posterior commencement of the 

 middle condyle projects further and more abruptly in No. 1585 than in 

 No. 1567 ; the posterior part of the distal half of the bone is less 

 convex. 



The physiologist contending for a difference of age merely in the birds 

 to which the bones Nos. 1567 and 1585 belonged, must be prepared to 

 show that in other large Struthious birds the tarso-metatarsal bones alter 

 in their proportions as well as their size in the progress of growth, and 

 that they are thicker and more robust in the young than in the old birds. 

 The contrary however is the case in the Ostrich and the Common Fowl. 

 In the great existing Struthious bird more especially, which offers the 

 most instructive analogy in the present comparison, the tarso-metatarsal 

 bone is relatively more slender in proportion to its length in the young 

 bird than in the old, at least at the period of growth when the tarso- 

 metatarsal bone has attained two-thirds its full size, which is precisely 

 the proportion which the bone of the Dinornis No. 1574 bears in length 

 to the bone No. 1567- 



3a2 



