244 PROFESSOR OWEN ON THE GENUS DINORNIS. 



individual of the same species of Dinornis as that to which the great tarso-metatarsal 

 bone m 1 belonged, virtually assumes that the relations which modify the progress of 

 ossification were different in the Dinornis from what they are in the Ostrich, and that a 

 bird which, from the non-extension of the air-cells into the femur, was as poorly en- 

 dowed with powers of flight as the Apteryx, and consequently possessed of as compara- 

 tively low circulating and respiratory energies, must at the same time have enjoyed as 

 rapid an ossification of the skeleton as the Swallow ; postulates which, being contrary 

 to known physiological correlations, are inadmissible. 



Since, therefore, the tarso-metatarsal m 3 combines with the characters of a fully de- 

 veloped bone, a marked difference of size, different proportions, and some minor modi- 

 fications of form, as compared with the large bone m 1 , it must indicate a second species 

 of Dinornis, which, as it attained, as will be presently shown, the average height of the 

 y. Ostrich {Struthio camelus), I shall call Dinornis struthoides. '~'^ 



That the Dinornis struthoides is in fact a good and true species, is put beyond all 

 cavil or doubt by the existence of a tarso-metatarsal bone (m 2)' which is longer than 

 m 3, but agrees in the proportions and form of its shaft with m 1 , and manifests the 

 same characters of immaturity which have been already noticed in the corresponding 

 bone of the young Ostrich. Here, therefore, we actually have, what m 3 might have 

 been mistaken for, a bone belonging to a young individual of the gigantic species 

 a' {Dinornis giganteus). 



Tlie condition of this young bone demonstrates, what could not indeed be reasonably 

 doubted, that a more tardy ossification coexists in the Dinornis, as in other Struthionida, 

 with the absence of the powers of flight ; and as such a condition in the present bone 

 establishes the maturity of the tarso-metatarsal bone m 3, which it exceeds in length, 

 it proves, a fortiori, that the smallest tarso-metatarsal, with all the characters of mature 

 age, could not have belonged to a young individual of either of the two larger species. 

 Or, in other words, if the young of the Dinornis giganteus, when the shaft of its tarso- 

 metatarsal bone is eleven inches long, manifests evident marks of immaturity, these 

 characters ought to have been more strongly marked in the shorter tarso-metatarsals 

 m3^ and m 5^, if they had really belonged to young individuals of the largest species. 

 The marks of immaturity in the shaft of the tarso-metatarsal of the young Dinornis gi- 

 ganteus, m 2, are the gradual deepening and widening of the anterior median channel of 

 the shaft as it approaches the proximal end of the bone, until it divides into the fissures 

 separating the proximal ends of the three constituent metatarsals, which extremities in 

 the specimen are broken off immediately above the point where they begin to coalesce. 

 In a specimen of the tarso-metatarsal bone, m 6, of the Dinornis didiformis, in which the 

 proximal end is broken off a few Hnes above the anterior rough depression which indi- 

 cates the primitive dividing groove, the constituent metatarsals are faintly indicated by 



I PI. XXVIII. fig. 3. ' lb. fig. 5. 3 lb. figs. G & 7. 



