78 
DR. W. KOWALEVSKY ON THE 
second and third cuneiform, is only a question of time, the modification going on unin- 
terruptedly in the direction of the greater reduction of the limb-bones. 
Can the general tendency of this steady reduction be doubtful 1 Is not the fact 
eloquent enough, that, proceeding from the middle Miocene times until the recent 
period, we meet with a whole series of Suina in which the skeleton is gradually more and 
more reduced, until it culminates in the Post-tertiary time in Dicotyles, a form very 
analogous, in the structure of its limbs, to the Ruminants, whose middle digits are quite 
ready to coalesce into a cannonbone, and the laterals to drop off"? Indeed, this has begun 
in the posterior limb, in which reduction is always in advance, and on its outer side, which 
is generally more reduced than the inner. If any inference from one series of pheno- 
mena is allowed to be applied to another, then, inasmuch as the Paridigitata with cres- 
centic teeth, or the recent Ruminantia, proceeding from tetra- or even pentadactyle 
forms, arrived in the Miocene period at didactyle forms, in which the coalescence of 
the two middle digits simulates monodactylity, we have a full right to infer, seeing 
the parallelism of these two groups, that the Paridigitata with tubercular teeth 
have followed just the same line of reduction. And if nature should be allowed to 
follow its course, or if man had made his appearance only in the Post-quaternary instead 
of the Post-tertiary period, he would no doubt have found only two groups of Pari- 
digitates remaining, one with crescentic, the other with tubercular teeth, but both having 
a cannonbone in their fore and hind limbs, and no lateral digits. These two groups 
of Paridigitates undergo exactly parallel modifications in the course of time, as far as 
their limbs are concerned — only in the group with crescentic molars these modifications 
have gone on much more rapidly than in the parallel group with tubercular teeth. The 
cause of this greater rapidity lay very probably in the more specialized, instead of an 
omnivorous, diet, and was perhaps influenced by the commencing faculty of rumination, 
which gave them an enormous advantage over the other group, by allowing them to 
store food in their paunch in the most favourable, or least dangerous, part of the day, 
and chew it afterwards when retiring to rest. 
If we turn now to the Paridigitates with crescentic teeth, represented in our times 
only by the living Ruminantia, we meet in the typical (which in this case means the 
most reduced) genera both middle metacarpals and metatarsals coalesced so as to simu- 
late a monodactyle foot, forming the so-called cannonbone. The rudiments of the 
lateral digits are mostly lost (in Bom dm and Antilopidoe ) or retained only as small 
filaments of bone, having no articulation with the carpal or tarsal bones, but merely 
pressed to the outer and inner sides of the two middle digits. The trapezium is 
entirely lost ; the trapezoid is confluent with the magnum *. In the tarsus, the navicular 
is confluent with the cuboid, and the second cuneiform with the third ; the first remains 
nearly always separate, and in case of confluence with the coalesced second and third 
cuneiforms, as in the Giraffe, the division is clearly seen. This is the general structure 
of the foot in the typical Ruminantia, or the most reduced Paridigitata with crescentic 
* Except in C'amelidce. 
