HISTORY OF THE CARNIVORA 537 



the face was less abbreviated ; the resemblance to 'fSmilodon 

 was very marked in the form of the cranium, but, of course, 

 the skull of "^HoplopJioneus was distinctly more primitive in 

 many respects. Thus, the orbit was much more widely open 

 behind, the tympanic bullae were but imperfectly ossified, and 

 the perforations, or foramina, in the base of the skull, by 

 which the nerves and blood-vessels communicated with the 

 brain-chamber, were quite different and had more resemblance 

 to those of the ancient dogs (e.g. '\Daphoenus). In the classi- 

 fication of the Fissipedia much stress is laid upon the number 

 and arrangement of these cranial foramina, and it is very 

 significant to find the primitive dogs and cats agreeing so 

 much more closely than do the modern members of these 

 families. The lower jaw was relatively much stouter than in 

 "fSmilodon and the anterior flanges much more prominent, 

 projecting downward so far that, when the jaws were closed, 

 the points of the tusks did not extend below the flanges. 

 The animal could have made no use at all of the sabre-tusks 

 unless the mouth could have been opened so widely as to clear 

 their points. 



With close general resemblance, allowing for the very inferior 

 size, the skeleton of "fHoplo phone us had many significant differ- 

 ences from that of 'fSmilodon. The neck was shorter and the 

 body, especially the loins, longer, lighter and more slender and the 

 tail very much longer, equalling that of the Leopard in relative 

 length and surpassing it in thickness. The limbs were much 

 less massive and somewhat differently proportioned, the upper 

 arm being shorter and the fore-arm longer. The humerus, 

 though far more slender than that of "{Smilodon, was remarkable 

 for the great development of the deltoid and supinator ridges, 

 the latter, together with the shape of the radius, indicating 

 very free rotation of the fore paw. The very prominent in- 

 ternal epicondyle was pierced by a foramen, and the femur had 

 a distinct remnant of the third trochanter. The five-toed 

 feet were comparatively small, but the claws were as completely 



