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 Fvlide, 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 
Hluroidea, 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 Curnivora,” Prov. Zool. Soc. 1869, p. 4; Mivart, 
“On the Classification and Distribution of the Elurcidea,” ibid. 1882, pp. 135 
and 459; see also The Cat, an Introduction to the Study of Backboned Animals, 
especially Mammals, vy the same author, 1881. 
