PEOFESSOE OWEN ON THE GENFS DEOMORNIS. 187 



scribed, under the name of Dromornis australis, in volume viii. of the Transactions of 

 the Zoological Society, p. 381, pis. 62, 63. 



In the first difference which I note in the Australian fossil tibia the bone resembles 

 that of Gastornis and differs from that of Dinornis, viz. in the medial position of the 

 ' precondylar groove ' ^ (PI. XXXIII. fig. l,^j). In every species of Dinornis this groove 

 is near the inner (tibial) margin of the fore part of the bone (see plate cit. note 1, 

 and Trans. Zool. Soc. vol. viii. pi. 59. fig. 1, p, Dinornis gravis). In both Dinornis 

 and Gastornis the groove is crossed by a bridge of bone. Of this bridge there is no trace 

 in the present Australian fossil, and there is no evidence of fracture of the piers of such 

 a bridge. The margins of the groove whence the bridge springs in Dinornis are, in 

 Dromornis, broadly convex and entire. Dromaius and Casuarius " have the precondylar 

 groove, but not the bridge. In both the groove is not medial, as in Dromornis, but is 

 nearer the inner border of the tibia, less near, however, than in Dinornis. In Struthio 

 there is neither groove nor bridge ; but in place of the groove there is a transverse rising 

 of the bone. Apteryx offers a miniature resemblance to Dinornis in this tibial character. 



The distal expansion is relatively less, in comparison with the shaft of the tibia, in 

 Dromornis than in Dinornis elephantopus (the species which Dromornis most resembles 

 in the size of the shaft). The inner border of the distal end of the shaft (PI. XXXIII. 

 fig. 3, «)is broader than in Dinornis, in which it contracts almost to a ridge as it passes 

 to the beginning of the posterior production of the inner (tibial) condyle. InDromornis 

 the corresponding part of the shaft, a, maintains a smooth transverse convexity to the 

 condyle s. The anterior production of the inner boundary of the rotular part of the 

 intercondylar space (ib. fig. 2, b) is more prominent in Dromornis than in Dinornis. 

 The hind part of the inner condyle (ib. fig. l,s) is less produced than in Dinornis; 

 and the corresponding part of the outer condyle, t, is less convex. There is no 

 definite cavity below the precondylar groove for the antentocondylar^ prominence of 

 the metatarse. 



There are other minor differences; but the above-defined patent ones sufiiciently 

 establish the fact of a nearer resemblance in the tibia, as in the femur, of the gigantic 

 wingless bird of Australia to the genera still there represented (Dromaius and Casua- 

 rius), than to Dinornis, Apteryx, or Struthio. 



The following are comparative admeasurements : — 



r, ■ Dinornis n, ,-, ■ 



JJromorms. , j j . -, binithio. 

 {ele/ihantopus). 



Transverse breadth of the shaft of the tibia at m. lines. in. lines. in. lines. 



the commencement of the distal expansion .22 28 15 



Ditto ditto distal condyles .35 40 29 



The fossil above described is in a more mineralized condition, consequently of greater 



> Anat. of Vertebrates, ii. p. 78. = Osteol. Catal. Mus. Coll. Surg. 4to, 1853, vol. i. p. 250. 



' See Trans. Zool. Soc. vol. vii. fig. 3, c. 



VOL. x.^PART III. No. 8. — October Jst, 1877. 2 d 



