44. AFFINITIES [Parr I. 
demonstrative of its affinity to the Colwmbide, and of its remoteness from the Raptores. But 
as these will form the subject of the second part of this work, and will there be treated m full 
detail by Dr. Melville, I will only briefly enumerate the more important ones. ‘These are :— 
18, the absence or non-development of the vomer, and of the bony septum of the nostrils ; 
19, the long narrow nasal fissures ; 20, the form of the posterior facet of the lower jaw ; 21, the 
oblique direction of the zygomatic bone ; 22, the peculiar form of the palatine bones; 23, 
the mesiak occipital foramen above the foramen magnum, (peculiar, it would seem, to the 
Pigeons and the Dodo); 24, the breadth and peculiar twist of the metatarsal of the hind toe 
(see Plate XI.); 25, the oval transverse section of the tarso-metarsal; 26, the peculiar form 
of the upper extremity of the tavso-metatarsal, including the arrangement of the calcaneal 
processes, and of the canals for the passage of the flexor tendons; and 27, the fact (peculiar 
to the Pigeons and the Dodo) that these canals pass on the owtsede of the posterior ridge of 
the tarsus, and not on the zzséde, as in Gallinaceous birds. 
Such are the principal points of agreement between the Dodo and the Pigeon family, 
and it will be admitted that they are neither few nor trivial. ‘There are, however, two or 
three points of diversity which it is only fair to mention. 
1. I need only allude as a matter of form to the non-development of wings, as it is admitted on 
all hands that this character distinguishes the Dodo from all other birds with which it can be legiti- 
mately compared, and is as much opposed to the normal structure of the Rapacious birds, as to that of 
the Columbide. 
2. The small size of the cranium in proportion to the beak distinguishes the Dodo no less from 
the Pigeons than from the Vultures. This peculiarity results from the small relative dimensions of the 
brain and eyes. It is a general law that animals of great magnitude (the Hlephant and Whale, for 
instance,) do not require those important organs to be enlarged in the same proportion as the parts 
destined for locomotion, and the nutritive functions. We need not, therefore, wonder that so colossal 
a bird as the Dodo should differ in this respect from other members of that family to which it is nearest 
allied. 
3. The Dodo is, as Professor Owen remarks, “peculiar among birds for the equality of length of 
the metatarsus and proximal phalanx of the hind toe,” while in most birds this phalanx is considerably 
longer than the metatarsal which supports it. The fact is, however, that no argument as to the 
general affinities of a doubtful ornithic genus can be drawn from the relative proportions of the tarso- 
metatarsal, the posterior metatarsal, and the proximal phalanx; these proportions varying in each 
genus according as its habits are more or less cursorial, ambulatory, or insessorial. A glance at 
Plate XI., where the forms of these bones in five different genera of Pigeons are exhibited, will sub- 
stantiate this remark. 
4. And, lastly, the nostril of the Dodo, although agreeing in position with that of Treron, is of a 
' This law is probably based on the distinction between ponderable and imponderable substances. The bones 
and muscles of an animal are mechanical structures, the size of which bears an exact arithmetical relation to the 
masses which they are required to move; but the eye and the brain have to deal with light and the nervous fluid— 
imponderable agents, to which the ordinary laws of mechanics do not apply. 
