PROFESSOR OWEN ON THE GENUS DROMORNIS. 187 
scribed, under the name of Dromornis australis, in volume viii. of the Transactions of 
the Zoological Society, p. 381, pls. 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’* (Pl. XXXIII. fig. 1, p). 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. Soe. vol. viii. pl. 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 Casuarius2 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. <Apteryxr 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 (Pl. XX XIII. 
fig. 3, a) 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. In-Dromornis 
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, 4) is more prominent in Dromornis than in Dinornis. 
The hind part of the inner condyle (ib. fig. 1, s) is less produced than in Dinornis: 
and the corresponding part of the outer condyle, ¢, 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 sufficiently 
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 :— 
D b Dinornis . 
romornis. 5 Struthio. 
ee (elephantopus). 
Transverse breadth of the shaft of the tibia at in. lines. — in. lines. in. lines, 
the commencement of the distal expansion. 2 2 ae 1h 
Ditto ditto distal condyles . 38 65 A50) NY 
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 111. No. 8.—October 1st, 1877. 2D 
