HIGH SCHOOL ZOOLOGY, 177 



the weight of the body i-ests entirely on the tips of the 

 third and fourth toes, being transmitted to them through a 

 cannon bone, which is formed by the more or less complete 

 coalescence of the third and fourth metapodials (Figs. 115' and 

 110 O). There are generally horns in this group, often con- 

 fined, however, to the male sex ; when there are no horns, 

 tusk-like canines may serve as compensatory weapons of de- 

 fence. The sheep, oxen, antelope and deer are tlie ty])ical 

 ruminants, but there are some aberi-ant families which we may 

 shortly consider first. 



Of these the Camelidce present some peculiar features ; for example, 

 the psalterium is absent ; the upper jaw in front is not destitute of teeth, 

 for it retains one of the upper incisors and the canine on each side, 

 which are absent in the ruminants : the canines, the upper especially, are 

 tusk-like and the molars are only | Instead of walking on the tips of 

 the digits, they are digitigrade forms, all three joints resting on the 

 ground ; the hoofs are thus of no use in locomotion, a single or double 

 pa<r of skin being present on the under surface of the third and fourth 

 digits. There are no dew-claws, but the third and fourth metapodials have 

 not so completely coalesced as in the oxen. The geographical distiibutiou 

 of the family has the same peculiarity which we have noted of certain 

 other groups, there being both Old and New World representatives, quite 

 isolated from each other at t.ie present day. In the Old World the genus 

 Camehts only occui's in a domesticated condition, as the Dromedary and 

 the Bactrian Camel, the former in Arabia, Africa, and India, the latter 

 (the two-humped camel), in the Mongolian table-lands. Both are used 

 as beasts of burden, and it is likely that the humps are the result of their 

 employment as such. There is only a single cushion underneath the 

 digits, Avhich, therefore, present a suitable surface for the sandy soil of 

 the desert. In the Kew World, on the other hand, there are both wild 

 and domesticated forms belonging to the genus Aiichenia ; these are 

 smaller sized forms without a hump, they tread on a double pad, 

 have fewer molars and larger ears than the camel. The wild species are 

 the larger Huanaco, and the smaller Vicuna ; the domesticated forms, the 

 Llama (the beast of burden of the mountain regions of Peru), and the 

 Alpaca, which is kept in herds for its flesh and its wool. The explanation 

 for the existence of the two branches of this family is to be sought in the 

 Miocene Strata of America, where numerous remains of CameLd» are 



