MAMMALS—CANIDAE—VULPES FULYUS. 129 
The skull of the red fox has the usual physiognomy of the American Canidae, and in fact is 
a miniature of that of the prairie wolf, from which it differs by characters hereafter to be 
pointed out. The resemblance to the skull of the gray foxes is much more remote. The upper 
profile undulates considerably ; the occipital outline is nearly perpendicular, but overhung by 
the occipital crest. The outline ascends rapidly from this point to above the meatus, where 
rounding over it slopes gently in nearly a straight line to a little beyond the post-orbital pro- 
cesses of the frontal bone, with a slight depression anterior to the temporo-frontal suture, and 
opposite the point of the post-orbital processes. The outline then curves rapidly downwards 
(convexly) to the point of the intermaxillary bone, then passes abruptly more horizontally to 
the anterior extremity of the nasals, the outline at the same time being quite convex. 
The temporal crests are not always united into one at the posterior portion of the parietal 
outline, and usually in the centre of an interparietal, which runs forward for a considerable 
distance, or about two-fifths of the length of the parietal; at this point they diverge in a very 
narrow lyre, approximating on the coronal suture, where they again diverge and pass forwards, 
continuous with the posterior edge of the post-orbital process. In old specimens the median 
sagittal or temporal crest extends to the coronal suture, when it diverges to the post-orbital 
processes as stated. There is a depression in the longitudinal line of the skull from between 
the points of the post-orbital processes to the middle of the nasals, and in a less degree to the 
end of these bones. There is also a considerable longitudinal swelling in the frontal bone on 
either side of this furrow. 
In the very great similarity in form of the skulls of the genus Vulpes, it is very difficult to 
assign any absolute characters which shall define the species with precision. Certain compari- 
sons with each other may, however, be made as serving to fix their distinctive features. Thus, 
the American red fox differs from that of the European Vulpes vulgaris (comparing eight of the 
one with five of the other) by a conspicuously more slender head and muzzle and less massive- 
ness of form. This will be at once shown by the table of measurements given previously. The 
muzzle is decidedly longer as well as more slender. The orbital processes are further back 
from the muzzle, and the distance from the posterior lower molar to the posterior portion of the 
‘condyle less. The palato-maxillary suture is not so far forward. 
The excess in length of the muzzle of the American red fox lies perhaps chiefly in the inter- 
maxillary, which projects further forward than in the European species, and has a wider gap 
between the incisors and the canines. ' 
The skull of the arctic fox, Vulpes lagopus, is shaped a good deal like that of the American 
red fox. It is somewhat smaller, however, and the muzzle more thickened at the base, and is 
much less contracted opposite the middle of the nasal bones, besides being considerably thicker 
at the end. The muzzle is much deeper, and its upper outline more horizontal; the inter- 
maxillary shorter in front of the canines, and its free margin much more nearly in a vertical 
line. The zygomatic arch is much higher and more curved, more deeply scooped out above in 
the orbital portion, and is narrowest opposite the middle of the molar, or on the middle of the 
anterior part of the arch instead of on the posterior portion just anterior to the glenoid cavity. 
There is no very striking difference in the teeth, except perhaps that the first tubercular upper 
molar (first true molar) in the Arctic fox is a little more deeply excavated, and the depressed 
ridge extending from the anterior internal tubercle to the low tubercle inside of the base of the 
posterior ‘external tubercle i is broken down. 
The differences between the skulls of Vulpes fulvus and macrourus will be more particularly 
17 L 
