308 SCOTT. [Vol. V. 



upon the rim of the orbit, and the foramen is single and placed 

 well within the orbit. 



The nasals are very long and narrow, and in general appear- 

 ance resemble those of the horse, but with some differences. 

 Posteriorly they are quite broad, reaching nearly to the antero- 

 superior margin of the orbit, and diverging so as to receive 

 between them the short and sharp nasal processes of the frontals. 

 In front of this expansion the nasals become very narrow, but 

 their sides are bent down nearly at right angles to the horizontal 

 portion, very much as in the horse. The free ends extend far 

 beyond the suture with the premaxillaries, and taper much less 

 rapidly than in Eqims, their tips being rounded and blunt, not 

 sharp points. 



In correspondence with the small size of the incisor teeth, the 

 alveolar portion of the premaxillaries in Mesohippus is but feebly 

 developed and is conspicuously smaller transversely, and more 

 especially in the vertical diameter than in Eqims: the ascending 

 ramus is much shorter and less obliquely directed than in the 

 horse ; it forms a thin and narrow plate and has a short contact 

 with the nasal. The anterior nares are much lower and nar- 

 rower than in the horse. The palatine plates of the premaxil- 

 laries are very small, and the spines much more slender and very 

 much shorter than in the horse, as are also the anterior palatine 

 foramina. 



The maxillaries are chiefly remarkable for their small extent 

 vertically, especially of the alveolar portion, which is very low, 

 so that the inferior rim of the orbit is brought very near to the 

 molars ; but even the portion which is applied to the formation 

 of the nasal chamber is much less extended vertically than in 

 the existing species. There is a short diastema between the 

 canine and the first premolar, and just in front of the latter the 

 face is slightly constricted. The maxillary is also much shorter, 

 proportionately, than in the modern forms, in correlation with the 

 much smaller size of the molars. The alveolus is extended some 

 distance behind the last molar, but less than in Equus, and there 

 is a well marked notch between the palatine and this portion of 

 the alveolus. The palatine processes of the maxillaries are 

 narrow and quite short, which is brought about by the position 

 of the posterior nares, which extend as far forward as the first 

 molar, and thus have a much more anterior situation than in the 



