398 THE OSTEOLOGY OF VULPES MACROTIS. 



The Skull. 



Both the skull (Plate XXII, figs. 1-7) of Vulpes macrotis as well as that of 

 V. velox before me, belonged to individuals that had not full} 7 reached maturity. 

 This is clearly proven by the fact that both the cranial and the facial sutures are 

 still very evident and easily traced. This is also the case with one of my skulls 

 of Cants latrans, while in another skull of the same species the sutures are all 

 nearly obliterated, while other evidences of advanced age are present. These 

 changes are well known to students of mammalian osteology, and are sometimes 

 very remarkably exemplified : the skulls in extremely old individuals varying 

 widely in their external appearances from those of subadult specimens of the same 

 species, and to an extent to sometimes almost lead to the belief that the animals to 

 which they severally belonged were not of the same species. This is a fact that 

 palaeontologists bear well in mind, and there are instances upon record where mis- 

 takes, due to the non-appreciation of these changes, have occurred. 4 The manner 

 in which they effect the appearance or morphology of the temporal fossae and 

 sagittal crest in the Canidse has already been noticed above, and it remains but to 

 say that during their progress there is no appreciable change either in form or 

 appearance of the brain-case within. These changes occur in many mammals, and 

 are particularly noticeable in the elephant. 



Viewed upon its superior surface it will be seen that the Cranium of Vulpes 

 velox has a subglobular form with the temporal areas slightly roughened, and the 

 extensive shield-shaped sagittal area quite smooth. The apex of the latter is 

 towards the interparietal bone, and the sagittal crest is barely perceptible, even 

 posteriorily, where in Canis latrans it is very conspicuous. In both Vulpes ma- 

 crotis and V. velox the coronal suture and the posterior two thirds of the sagittal 

 exhibit interlocking serrations of the apposed margins, a condition that likewise 

 obtains in the frontal suture of the skull of V. velox. 



All the other sutures upon this aspect of the skull in these two foxes, as well 

 as in the coyote, have smooth margins, especially the nasal and inter-nasal ones. 

 Either post-orbital process is well developed, being a triangular ledge of bone, with 

 its apex directed backward and outward, and its superior surface showing a 

 decided depression, better marked in macrotis than in velox, while in Canis latrans 

 it is not present at all, that surface being rounded, and the process, bluntly pyra- 

 midal in form, extending directly outward. Proportionately, the skull in V. 

 macrotis is longer and narrower than it is in V. velox, and this is well seen in its 

 facial portion on the surface we are now considering, where in the first-named fox 

 this feature is markedly the case. 



4 In this connection Flower has said that these changes or modifications " depend mainly on the 

 fact that the brain, and consequently the cavity which contains it, and also the sense capsules, increase 

 in size in a much smaller ratio than the external parts of the head, especially the jaws and prominences 

 for the attachment of muscles. The disproportionate growth and alteration of form of these parts, 

 concomitant with little or no change in the brain-case, is effected partly by increase in thickness of the 

 bones, but mainly by the expansion of their walls and the development of cells within, which greatly 

 extend the outer surface without adding to the weight of the bone." — Osteology of the Mammalia, 3d 

 Ed., p.. 148. 



