318 PROFESSOR OWEN ON THE GENUS DINORNIS. 



In the Emeu {Dromaius) the sternum {ib. fig. 7) , with the same general form as in 

 the Cassowary, further differs from that of the Dinornis in the approximation of the 

 coracoid grooves (ib. c, c) so as to come into actual contact at the middle of the anterior 

 border. 



Of the sternum of the Dodo we as yet unfortunately know nothing, although we may 

 as reasonably expect the osseous remains of that extinct bird to reward the search of 

 naturalists and collectors in the islands of Mauritius and Rodriguez, as the similar quest 

 in New Zealand has been followed by the recovery of the bones of the Dinornis. 



In the Apteryx however we find a sternum [ib. fig. 8), which, with the same general 

 Struthious characters, very closely corresponds with the particular modifications of that 

 of the Dinornis. It has the same small proportional size to the body ; nearly the same 

 superior breadth as compared with the length, the same sUght degree of convexity, and 

 the same characteristic expansion and marginal configuration posteriorly. In the sternum 

 of the Apter^TC described and figured in the Zoological Transactions, vol. ii. p. 290, pi. 55. 

 figg. 2 & 3, two small subcircular spaces remained unossified in the body of the sternum ; 

 in two more mature specimens which I have subsequently received, ossification has ob- 

 literated these spaces, where however the bone is thin and diaphanous, and the sternum 

 presents only the two deep posterior emarginations, bounded by a middle xiphoid pro- 

 longation and the two angular elongated processes (p, p), as in the Dinornis. These 

 processes in the Apteryx are relatively broader, thinner, and are subincurved : in the 

 Dinornis they seem, from the remains of the one on the left side, to be straight, and 

 become thicker and narrower. 



The costal articular surface occupies a greater proportion of the lateral margin of the 

 sternum in the Apteryx than in the Dinornis, though it is less than in the Ostrich. The 

 coracoid groove has the same relative position and size in the Apteryx as in the Dinornis, 

 but has a different form : in the small existing wingless bird it is an obUque notch, 

 formed by a small process projecting upward and forward from the outer surface of the 

 sternum near the antero-external angle : in the Dinornis {ib. fig. 2, c) it is an oblique 

 depression, as if the end of the thumb had been pressed into the same part of the bone 

 when soft. The anterior and lower border of the depression is not produced beyond the 

 level of the bone ; but in the example before me it is notched, as if for the passage of 

 vessels to the joint. 



Whether the antero-external angle (a) is prolonged so far in Dinornis as in Apteryx, 

 the fracture of that part in the present specimen does not allow to be determined. The 

 anterior margin between the coracoid articulations in the Apteryx is deeply excavated, 

 whilst in the present species of Dinornis it is almost straight. Four smooth depressions 

 with three well-marked rough surfaces (r, r', r") for the attachment of sternal ribs, cha- 

 racterise the anterior two-thirds of each lateral border in the Dinornis. The outer sur- 

 face of the sternum in the Dinornis shows the impressions of the decussating bands and 

 fibres of the aponeurotic periosteum, with which it was covered when recent. 



A part of a young Apteryx, which I owe to Dr. Robert Hunter, demonstrates that 



