500 CARNIVORA 



say, the ungual phalanx, with the claw attached, folds back in 

 the fore foot into a sheath by the outer or ulnar side of the middle 

 phalanx of the digit, being retained in this position when the 

 animal is at rest by a strong elastic ligament In the hind foot the 

 ungual phalanx is retracted on to the top, and not the side of the 

 middle phalanx. By the action of the deep flexor muscles, the 

 ungual phalanges are straightened out, the claws protruded from 

 their sheath, and the soft " velvety " paw becomes suddenly con- 

 verted into a most formidable weapon of offence. The habitual 

 retraction of the claws preserves their points from wear in ordinary 

 progression. 



The skeleton of the Lion represented in Fig. 15 (p. 45) illus- 

 trates the digitigrade mode of progression of the Fetidce, as well 

 as the essential characters of the bony framework of a typical 

 Carnivore. 



The Fissipedal Carnivora were divided by Cuvier into two 

 groups, according to the position of the feet in walking, the 

 Plantigrada, or those that place the whole of the soles to the 

 ground, and the Digitigrada, or those that walk only on the toes ; 

 and the difference between these groups was considered of equal 

 importance to that which separated the Pinnigrada or Seals from 

 both of them. The distinction is, however, quite an artificial one, 

 since every intermediate condition exists between the extreme 

 typical plantigrade gait of the Bears and the truly digitigrade walk 

 of the Cats and Dogs ; in fact, the greater number of the Carnivora 

 belong to neither one form nor the other, but may be called 

 " subplantigrade " ; often when at rest applying the whole of the 

 sole to the ground, but keeping the heel raised to a greater or less 

 extent when walking. 



An amended classification of the existing forms is into three 

 distinct sections, of which the Cats, the Dogs, and the Bears may be 

 respectively taken as representatives, and which are hence called 

 ^Eluroidea, Cynoidea, and Arctoidea. This division is founded 

 mainly on characters exhibited by the base of the skull, but is 

 corroborated by the structure of other parts. 1 The presence or 

 absence of a bridge of bone, covering the external carotid artery in 

 a part of its course by the side of the alisphenoid bone, and enclosing 

 the " alisphenoid canal " (see Fig. 8, p. 38), a character to which the 

 late Mr. H. N. Turner first drew attention, might seem unimportant 

 at first sight, but it is curiously constant in certain groups, which 

 we have other reasons, derived often from a combination of less 



1 See Flower, " On the Value of the Characters of the Base of the Cranium 

 in the Classification of the Order Carnivora," Proc. Zool. Soc. 1869, p. 4 ; Mivart, 

 "On the Classification and Distribution of the ^luroidea," ibid. 1882, pp. 135 

 and 459 ; see also The Cat, an Introduction to the Study of Backboned Animals, 

 especially Mammals, by the same author, 1881. 



