of the Genus Stenomylus. 301 



in front of the orbit, is an oval depression some 25 mm long by 

 12 mm high, and so deep that between the two sides there is bnt 

 9 mm , which must nearly close the olfactory space within the 

 muzzle. In like manner the subnasal pit is well down on the 

 side of the snout, and extends from over premolar 1 to over 

 premolar 4, being about the same size as is the preorbital pit. 

 In the latter case the depth of the pits is, however, such that 



Fig. 2. 



there is but six millimeters between the two sides of the skull 

 opposite the bottom of the pits, so they must practically close 

 the internal olfactory passage in that vicinity. Similar, though 

 less developed, pits occur in other primitive genera among the 

 Tylopoda : and the preorbital pit. is also characteristic of several 

 species of horses of the Oligocene genus, Mesohippus. The 

 pits were probably occupied by glandular structures, but pits 

 of such extent are not known to the writer among recent 

 genera. The pit occupied by odor-secreting glands among cer- 

 tain artiodactyls may be cited as a counterpart, but it is hard 

 to believe that odor glands in any species became as large as 

 those pits would indicate. 



As is usual for members of the tylopod phylum, there is an 

 orbital vacuity of some extent at the juncture of the maxilla, 

 nasal and lacrymal bones. The lacrymal bone itself is rela- 

 tively large, extending considerably in front of the orbit. The 

 margin of the orbit is sharply outlined and smooth except that 

 on the lacrymal there are two deep and characteristic notches. 

 The lacrymal foramen is well within the border of the orbit. 

 The jugal bone bounds the front and lower part of the orbit, 

 meeting in the rear the broad postorbital process of the frontal. 

 The squamosum is of moderate dimensions, and carries a 

 slender zygomatic process. On the lower surface the glenoid 

 articular surface can scarcely be described as a cavity, making 



