86 MOSTLY MAMMALS 



Strange as are the foregoing creatures, they are exceeded 

 in this respect by the long-necked and long-limbed animal 

 named Macrauchenia (on account of the elongation of the 

 vertebrae of the neck), specimens of which were first 

 brought back by Darwin from the superficial deposits of 

 Patagonia. In general form the macrauchenia somewhat 

 recalls a camel ; and it is a curious circumstance that, in 

 common with that animal and its allies, it differs from all 

 other ungulates, with the exception of certain kindred 

 Argentine forms, in that the arteries of the neck pierce 

 the sides of the vertebrae to take a course within the 

 spinal canal, instead of passing merely through a loop of 

 bone on the exterior. This remarkable resemblance is not, 

 however, indicative of any affinity between the two animals, 

 since, if we look at the feet of the macrauchenia, we shall 

 find that they are of the odd-toed type, and each furnished 

 with three digits. Moreover, the huckle-bone has the 

 pulley-like upper surface characterising the odd-toed ungu- 

 lates ; and as the teeth approximate to those of the latter, 

 we might be inclined to place the creature in that group. 

 The wrist- and ankle-joints are, however, formed on the 

 linear plan, and exhibit certain other departures from the 

 odd-toed type, and it is therefore evident that the macrau- 

 chenia and its allies constitute a third group of extinct 

 ungulates peculiar to South America. Although it is by 

 foot-structure that the macrauchenia is separated from all 

 other members of the order, its most remarkable peculiarity 

 is to be found in the structure of its skull. In an ordinary 

 mammal the aperture of the nose is situated quite at the 

 anterior extremity of the skull. In the macrauchenia, on 

 the other hand, this aperture forms an egg-shaped vacuity 

 in the forehead, almost between the eyes. Some approxi- 

 mation to this remarkable arrangement is presented by 



