414 UNGULATA 



trochanter of the femur was aborted. These huge animals 

 inferior in size only to the Elephant appear to have been abundant 

 in the United States during the Miocene period. 



Family MACRAUCHENIID.E. 



This extinct South American family is best known by the genus 

 Macrauchenia, as represented by M. patachonica and M. boliviensis, 

 Avhich are apparently from Pleistocene formations. They are very 

 singular and specialised forms, quite out of the line of descent of 

 any of the existing Perissodactyles, and the steps by which they 

 are connected with the rest of the group have not yet been 

 discovered. Of the larger species, M. patachonica, the skeleton is 

 completely known. It had the full number of forty-four teeth, 

 forming an almost uninterrupted series. The cervical vertebrae 

 resemble those of the Camels in the position of the vertebrarterial 

 canal, but the ends of the centra are flat, and not opisthocoelous as 

 in the allied forms. In some of the limb characters it resembles 

 the Equidce, but in the articulation of the fibula with the calcaneum 

 it agrees with the Artiodactyles. The structure of the feet is, 

 however, distinctly Perissodactylate, there being three toes on each. 

 The teeth approximate to a Rhinocerotine structure ; and the incisors 

 have an infolding of the enamel of their crowns, as in those of the 

 Horses. The nares open on the top of the skull, and it is probable 

 that the muzzle was produced into a short proboscis. Several 

 other South American forms have been referred to this family, 

 some of which have received distinct generic names, but further 

 evidence is required before many of them can be accepted. Pos- 

 sibly Homalodontothemim should be placed here. 



Family PROTEROTHERIHLE. 



Proterotherium. Here may be noticed certain very remarkable 

 Perissodactyles from the South American Tertiaries, for which the 

 name Proterotherium has been proposed. The cheek-teeth are so 

 like those of Anchitherium that they have been described under 

 that name. The upper jaw has one pair of canine-like incisors and 

 no canines, while the lower jaw carries two pairs of incisors. In 

 the skull the orbits were completely closed, as in the Horses. The 

 feet were tridactyle, like those of Hipparion, but the tarsus was 

 constructed on an Artiodactyle type. 



SUBUNGULATA. 



By far the greater number of the Subungulata are extinct, and 

 of many of those whose former existence has been revealed, chiefly 

 by the labours of the American palaeontologists, our knowledge is 

 at present necessarily imperfect, though daily extending. It will 



