490 LAND MAMMALS IN THE WESTERN HEMISPHERE 



same division of the Pachydermata with the rhinoceros, tapir, 

 and palseotherium ; but in the structure of the bones of its 

 long neck it shows a clear relation to the camel, or rather to 

 the guanaco and llama." ^ The views upon classification and 

 relationship here expressed have been superseded, but the 

 passage is an important one in the history of scientific opinion. 



'\Macrauchenia (Fig. 120, p. 216), as Darwin says, was as 

 large as a camel ; it had an unreduced dentition of 44 teeth and 

 in each jaw the teeth were arranged in continuous series and 

 were quite decidedly hypsodont. Both in the upper and the 

 lower jaws the incisors formed a nearly straight transverse 

 row and have a "mark," or enamel pit, like that seen in the 

 horses ; the canines were but little larger than the incisors and 

 did not form tusks. The premolars were smaller and simpler 

 than the molars. The upper molars had two concave and 

 crescentic external cusps, connected by a median ridge, as in 

 several families of perissodactyls ; two transverse crests and 

 several accessory spurs and enamel-pockets gave to the grinding 

 surface, when somewhat worn, the appearance of considerable 

 complexity. The lower molars had the two crescents, one 

 behind the other, which recurred in almost all the South Ameri- 

 can types of ungulates ; the vertical pillar which so generally 

 in these types arose in the inner concavity of the posterior 

 crescent was wanting in the permanent teeth of ]Macrau- 

 chenia, but present in the milk-premolars. 



No part of this remarkable animal was more curious than 

 the skull, which was quite small in proportion to the rest of the 

 skeleton. It was long, narrow and low, sloping and tapering 

 forward to a blunt point at the end of the muzzle, though there 

 was a slight broadening here to accommodate the transverse 

 row of incisors. The sagittal crest was replaced by a short, 

 narrow and flat area ; the cranium was shortened and the face 

 elongated, the orbits, which were completely encircled in bone, 

 having been shifted behind the line of the teeth, as in the 



' Darwin, Voyage of a Naturalist, p. 172. 



