29 
orbital chambers are relatively, not absolutely, larger in the Solitaire. Taking the 
distance between the anterior and posterior orbital process in fig. 149, pl. 22 (N.), I find 
it three lines less than the same admeasurement in the skull of the Dodo in pl. 15 (O.). 
In like manner I discern no essential or generic difference of character in upper or 
lower mandibles of Pezophaps and Didus, only such modifications of shape and pro- 
portion as may differentiate such closely allied species. With the longer proportional 
metatarsals of the Solitaire goes a more slender and lighter-constructed beak (fig. 179, 
pl. 24, N.). The authors, however, note a “remarkable variation in the size of the 
upper mandible in different individuals, to the extent of very nearly one half the linear 
dimensions between the largest and smallest specimens, of which the collection contains 
thirteen in all,” Is there an intermediate gradational series? May this difference of 
length of beak concur with that pointed out by Strickland in the length of leg? 
Better specimens of the mandible of Pezophaps than had reached Messrs. Newton at 
the date of publication of their instructive memoir seem to be needed to solve these 
questions, and are indispensable for profitable comparison with that part in Didus 
(pl. 16. fig. 5x, text), The portions of the mandibular rami described and figured in 
N., however, serve to show an agreement with the maxilla in the more slender and 
less powerful proportions. It is interesting to note that the differences in size and 
proportion are less in the proximal than the distal elements of the mandible, 
No tympanic bone of Didus has yet reached me; so that I am unable to give figures 
of it separately, in order to compare with those of the Solitaire, figs. 163-168 in 
pl. 22 (N.), 
The atrophy of wings had not proceeded so far in the extinct Ground-Dove of 
Rodriguez as in the larger species of the Mauritius. The constituents of the scapular 
arch—scapula (pl. 19. figs. 97-99, N.) and coracoid (ib. figs. 76-79 )—are absolutely larger, 
or are relatively thicker or broader (pl. 19. figs. 152, 153) in Pezophaps than in Didus ; 
and the same difference of proportion preyails in the humerus, radius, and ulna. ‘The 
expansion of the distal end of the scapula in Pezophaps makes the general curve of the 
upper and anterior border slightly concaye; in Didus, beyond the proximal concavity 
of the curve of that border, it runs straight to near the distal end, towards which it 
curves, convexly, as in Pezophaps. The absence of any example of confluence of scapula 
and coracoid in the rich series of specimens possessed by Messrs. Newton of these bones 
(thirty-six of scapula, twenty-seven of coracoid) in the bird of Rodriguez, indicates a 
more habitual and powerful use of the appendage of the arch than was exercised by 
Didus. The halves of the slender furculum, which long remain separate in the Dodo, 
coalesce below earlier in the Solitaire. 
The bones of the manus of the Dodo are still unknown; the desire to obtain 
such is increased since the discovery that the metacarpus of Pezophaps has, on the 
radial border, a large subspherical knob resembling a tumour, and compared by its 
.N., p. 347. 
G2 

