360 MAMMALIA. 



shape, are somewhat spaced in the upper jaw. The ulna and radius, as 

 also the tibia and fibula, are fused together ; the metapodials are likewise 

 united into a cannon-bone on each foot, and there are no longer traces of 

 the lateral digits. Procamelus occidentalis (fig. 205) and other species occur 

 in the Upper Miocene (Loup Fork Series) of New Mexico, Dakota, Nebraska, 

 and Colorado ; probably also in Virginia and Florida. 



Camelus. The typical camels differ from Procamelus in the further 

 reduction of the dentition by the loss of one premolar in the upper, and 

 two premolars in the lower jaw. One or two species (Camelus sivalensis, 

 C. antiquus) are represented by numerous remains in the Lower Pliocene 

 of the Siwalik Hills, India ; and these are interesting as exhibiting a 

 vertical ridge at the antero-external angle of the lower molars, which is no 

 longer observed in the camels but characteristic of the South American 

 Auchenia. Fragmentary traces of other species have been recorded from 

 the Pleistocene of southern Russia, of Roumania, and of Algeria. 



Auchenia. The llamas, alpacas, vicunas, and guanacos of South 

 America are smaller and more slender animals than the existing camels, 

 with the two toes more distinctly separated. Their premolars are still 

 further reduced to two in each jaw. Remains of similar forms have never 

 been found in the later Tertiary deposits of the country they now inhabit 

 of earlier date than the latest Pliocene or the earliest Pleistocene. Two 

 very similar genera, with only one premolar in each jaw, are known by 

 fragmentary remains from the Upper Pliocene of Oregon, California, and 

 Mexico (Holomeniscus, Eschatius) ; and these are the latest representatives 

 of the Camelidse hitherto discovered in the land of their origin. 



The characters and mode of life of the earliest and most 

 primitive ruminants are probably revealed in the small existing 

 Tragulidae, or chevrotains, of the Indo- Malay an region and 

 western Africa. Palaeontology shows that these little animals, 

 unique and isolated among the Ungulata of the present day, are 

 the scarcely-altered survivors of a great tribe which flourished 

 abundantly in Europe, and less so in North America, before 

 the typical and fully differentiated ruminants had made their 

 appearance. The upper incisors have disappeared and the 

 foremost premolar is sometimes wanting; but otherwise the 

 dentition is complete, and the grinding teeth are in uninter- 

 rupted series. The upper molars bear the usual four crescentic 

 cusps, quite brachyodont; and the hindermost lower molar is 

 produced into a third posterior lobe. The basicranial axis is 

 straight. The tympanic bulla3 of the skull in the surviving 

 genera are filled with spongy bone. There are never any 



