OSTEOLOGY OF THE DODO. 517 
behind the acetabula—and the indications of “ prerenal,” “ midrenal,” and “ postrenal ” 
depressions—are all correspondences with the pelvis in Didunculus and Goura, which 
Pezophaps shows in common with Didus. 
The chief difference between Didus and Pezophaps in cranial structure is the degree 
iu which the cancellous tissue is developed between the outer and inner “ tables,” the 
minor quantity of that tissue in Pezophaps leaving a flatness of the frontals above the 
orbits contrasting with the convexity of that part of the cranium in Didus. 1 suspect 
that when the part of the skull of the Solitaire may be found, supplying what is 
wanting in the specimens figured in figs. 149, 150, pl. 22 (N.), there will be a depres- 
sion or concavity in the profile contour between the fore part of the frontals and the 
naso-premaxillaries, which will suggest the presence of a “frontal protuberance” dif- 
fering only in degree from that so called in Didus. Indeed Messrs. Newton recognize 
the fact that “the frontals rise abruptly as in Didus”}, the precise extent of the “rise” 
being yet to be determined in Pezophaps. A section of the cranium of a Solitaire, like 
that of the Dodo, in fig. 1, pl. 23 (O.), would, if it had been made and figured in N., 
have afforded ready means of judging of the degree and value of the difference in 
cranial structure of the two extinct Columbaceans. The orbital chambers are rela- 
tively, 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 interesting and instructive memoir seem to be needed 
to solve these questions, and are indispensable for profitable comparison with that part 
in Didus. 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.). 
N., p. 347. * N., p. 347. 
