MAMMALS CAJTIDAE VULPES FULVUS. 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 t 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 muz,zle 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 narroweat 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 is broken down. 



The differences between the skulls of Vulpes fulvus and macrourus will be more particularly 



WL 



