HISTORY OF THE fLITOPTERNA 495 



the first place, considerably smaller, not much exceeding a 

 llama in size ; the teeth had lower crowns than even those of 

 ^Scalihrinitherium and the incisors were arranged in line with 

 the grinding teeth, not in a transverse row, but curving inward 

 slightly, so that those of the opposite sides nearly met in 

 front. The incisors, canine and first premolar were simple, 

 sharply pointed, conical teeth, which gave an almost reptilian 

 expression to the anterior part of the skull. The upper molars 

 were on the same fundamental plan as those of jMacrauchenia, 

 but in a less advanced stage of development, the transverse crests 

 being incomplete and the internal cusps had a certain degree 

 of separateness from the crests and from each other. It is evi- 

 dent that the upper molars were derived from the quadrituber- 

 eular type. The lower molars had the vertical pillar in the 

 concavity of the posterior crescent very prominently developed. 

 The resemblance of the skull to that of fMacrauchenia is 

 obvious at the first glance, but it was less specialized and de- 

 parted less from the ordinary ungulate type. The cranium 

 was longer and the face shorter, the orbit, which was incom- 

 pletely closed behind, extending over the second molar. There 

 was a sagittal crest, the length of which differed much in the 

 various species ; the nasal bones were already very short, 

 though decidedly longer than in the subsequent genus '\Scali- 

 brinitherium, and the anterior nasal opening Vv^as extended 

 forward as a long, narrow slit, because the maxillaries did not 

 come into contact with each other in the superior median line, 

 and the premaxillaries touched each other, but were not co- 

 ossified. The nasal canal, though very short, was horizontal, 

 not vertical. The skulls of the three genera thus displayed 

 three successive stages in the backward shifting of the orbit 

 and of the anterior nasal opening, in the shortening of the 

 nasal bones and in the formation of a solid rostrum by the 

 fusion of the upper jaw-bones. No doubt also the living ani- 

 mals exhibited a corresponding gradation in the development of 

 the proboscis. 



