_Skull._--The individual bones, especially those at the base, do not differ in shape. But the whole skull, in its proportions, outline, and relative direction of the bones, differs greatly in some of the breeds, as may be seen by comparing the figures of (A) the wild rock-pigeon, (B) the {164} shortfaced tumbler, (C) the English carrier, and (D) the Bagadotten carrier (of Neumeister), all drawn of the natural size and viewed laterally. In the carrier, besides the elongation of the bones of the face, the space between the orbits is proportionally a little narrower than in the rock-pigeon. In the Bagadotten the upper mandible is remarkably arched, and the premaxillary bones are proportionally broader. In the short-faced tumbler the skull is more globular; all the bones of the face are much shortened, and the front of the skull and descending nasal bones are almost perpendicular; the maxillo-jugal arch and premaxillary bones form an almost straight line; the space between the prominent edges of the eye-orbits is depressed. In the barb the premaxillary bones are much shortened, and their anterior portion is thicker than in the rock-pigeon, as is the lower part of the nasal bone. In two nuns the ascending branches of the premaxillaries, near their tips, were somewhat attenuated, and in these birds, as well as in some others, for instance in the spot, the occipital crest over the foramen was considerably more prominent than in the rock-pigeon. [Illustration: Fig. 25.--Lower jaws, seen from above, of natural size. A. Rock-pigeon. B. Runt. C. Barb.] [Illustration: Fig. 26.--Skull of Runt, seen from above, of natural size, showing the reflexed margin of the distal portion of the lower jaw.]