366 THE ANATOMY OF VERTEBEATED ANIMALS. 



in most respects, but lias only three digits in the manus as 

 well as in the pes. The dental formula, however, is 



i. -— c. -^ p.m. — m. — . The diastema is smaller than in 



the Tapir, and the patterns of the gi-inding teeth of both 

 jaws are more like those of the Rhinoceros. 



e. The Macrauchenidce. — The genus Macrauchenia is also 

 an extinct form, which occurs in later tex'tiary or quater- 

 nary deposits in South America. 



The feet are tridactyle, and the dental formula is 



i. -^ c. -^p.m. 777 w. jt;- The teeth are disposed in a nearly 



continuous series. The crowns of the incisors present a 

 deep fossa, as in the Equidce. The molars are in part 

 Equine, in part Rhinocerotic In character. The skull is, on 

 the whole, Equine, but the nasal bones are very short and 

 tapiroid. The vertebrae of the long neck are extraor- 

 dinarily similar to those of the Camelidce, and especially of 

 the Llamas. 



2. The Artiodactyla. — The number of the dorso-lumbar 

 vertebrae in this group is always fewer than twenty-two, 

 and rarely exceeds nineteen. 



The third digit of each foot is asymmetrical in itself, 

 and usually forms a symmetrical pair with the fourth 

 digit : and the functional toes of the hind foot are even in 

 number — that is to say, either two or four. 



The femur is devoid of any third trochanter ; the facets 

 upon the distal face of the astralagus are subequal, that 

 for the cuboid being nearly as large as that for the navicular 

 bone. The tympanic is large, and the pterygoid process 

 of the sphenoid is not perforated. 



The posterior premolar teeth usually differ a good deal 

 from the succeeding molars, being simpler in pattern. The 

 last milk molar in the lower jaw is trilobed ; but this is also 

 the case in some Perissodactyla. 



The stomach is more or less complex. The caecum, though 

 well developed, is smaller than in the Perissodactyla. 



The mammae are inguinal or abdominal. When horns are 



