ARTIODACTYLA, RUMIXANTIA. 587 



forms ; metacarpals and metatarsals 2 and 3 fused except in the oldest 

 forms ; cannon bone cleft below, digits with nails not hoofs, digitigrade on 

 cushion-like pads. Stomach 3-chambered, psalterium absent, riynen 

 smooth, with a number of diverticula with narrow openings which can be 

 shut off by a sphincter muscle from the stomach : these are the water- 

 cells and into them can pass the fluid of the stomach. The blood corpuscles 

 are elliptical. Placenta diffuse. Two living genera, Camelus L., camels 

 and dromedaries, dentition i ^ c \ p f m f , three incisors in upper jaw 

 in the young ; lower incisors procumbent; with one or two dorsal adipose 

 humps ; hairy not woolly, 2 species, Asia ; C dromedaries L., arabian 

 camel, one hump ; unknown in the wild state ; C. bactrianus L., 2 humps, 

 also domesticated but wild in Turkestan. Fossil species in U. Miocene 

 of India. Lama (Auchenia) G. Cuv., dentition i | c } p , r j ri m f ; 

 without hump, hair woolly, smaller than Camelus, they kick, bite, and 

 spit, and in their stomach are found bezoar stones ; 4 species usually dis- 

 tinguished, L. glama, the lama (not known in the wild state) ; L, pacos, 

 the alpaca ; L. huanacus, the guanaco, L. vicugna, the vicugna ; all in 

 S. America, the two first domesticated. Extinct species from Pliocene 

 and Pleistocene of Arner. Extinct genera from the Miocene onwards of 

 Amer. In Leptotragulus Scott and Osb., from the Eocene of Amer. with 

 3 premolars only in the lower jaw, there are 4 toes and the metapodia are 

 separate. Protylopus Wortm.,* Eocene, N. Amer., dentition complete, 

 orbit not enclosed, pes with digits 2 and 5 vestigial, about the size of a 

 rabbit. Poebrotherium t Leidy, Miocene of N. Amer., in form and size 

 resembling a small gazelle, has brachyodont, complete dentition, i f c \ 

 p $ m |, metapodials separate and remnants of metapodials 2 and 5. 

 Protolabis, Miocene, dentition as in the last. Procamelus Leidy, Miocene 

 and L. Pliocene of N. Amer. i c \ p $ m f , metapodia united and no 

 trace of lateral digits. No fossils of the Camelidae except those of the 

 genus Camelus have been found in the Old World. It has been held that 

 the extinct genera show less and less specialisation as Camelidae, the 

 older they are ; but this statement is only a rough approximation to the 

 facts. Leptotragulus 1 (Parameryx) which is found in the same beds as 

 Protylopus and has more complete outer digits, has a dentition more special- 

 ised not only than that of Protylopus but even than that of the later Protola- 

 bis, in the fact that there are only 3 lower premolars. Wort man (op. cit.) in 

 his account of the phylogeny of the Camelidae gets over this fact by 

 describing Leptotragulus as a " precociously specialised side branch 

 which died out at the close of the Eocene." Moreover Protylopus, which 

 by its small size and other features might be regarded as a primitive type, 

 possesses unfortunately hardly any trace of the outer digits in the pes. 

 This difficulty is got over by supposing that the manus, which is unknown, 

 possessed four digits (Wortman, op. cit., p. 137). 



Fam. 10. Tragulidae. Chevrotains. Hornless small animals, with 

 conical odontoid process, four complete toes (outer toes reduced), metapodia 

 of 3 and 4 uniting late, complete fibula ankylosed at its lower end with 

 the tibia, well developed canines, secant premolars, three-chambered 

 stomach and diffuse placenta. The premaxillae are edentulous, the lower 



* J. L. Wortman, The Extinct Camelidae of N. America, etc., Bull. 

 Amer. Mus., 10, 1898, p. 93-142. 



t Scott, Journ. Morpt., 5, 1891, p. 1. 



J Scott, Trans. Amer. Phil. Soc., N.S., 16, 1896, p. 479. 



Thomas, P.Z.S., 1891, p. 385. 



