154 ON THE EXTINCT MAMMALIA OF 



4. A small fragment of the right side of a lower jaw, containing three premolars 

 and the first molar. It belonged to a more aged, but ai^parently more robust indi- 

 vidual than any of the iDreceding specimens. The crowns of all the teeth, except 

 that of the second premolar, are nearly worn to their fangs. The second premolar, 

 represented and introduced in the series, figure 6, h, plate XV, has its crown worn off 

 about one-half, in an oblique manner posteriorly. It has widely divergent, robust 

 gibbous fangs. 



The space occupied by the four teeth in the fossil measures two inches and a half, 

 of which the premolars occupy twenty lines. 



5. A last premolar and the succeeding pair of molars of the right side of the lower 

 jaw. They belonged to a younger animal than an}' of the preceding specimens, and 

 agree in form with the corresponding fossil teeth previously described or indicated, 

 and also with those of the Camel. Upon the triturating surfaces of the premolar and 

 the anterior division of the first molar a small oval enamel pit is observable; on the 

 posterior division of the latter tooth, and on both divisions of the succeeding molar, 

 central crescentoid pits still remain. 



The measurements of the teeth at the triturating surfaces are as follow : 



Lines. 



Antero-posterior diameter of last premolar, . . . . .8 



Transverse diameter posteriorly, .. . . . . .4 



Antero-posterior diameter of first molar, . . . . .10 



Antero-posterior diameter of second molar, . . . . .14 



6. The alveolar portion of both upper maxillag, with part of the hard palate, and 

 containing most of the molar teeth much mutilated. 



The more perfect or left side of the specimen is represented in figure 7, plate XV, 

 with three premolars restored from the teeth of both sides, and the molars ideally 

 restored in outline. 



The roof of the mouth, as composed of the palatine plates of the maxillary and 

 palate bones, has nearly the same character as in the Camel. A large palatine fora- 

 men likewise holds the same relative position between the corresponding premolars. 

 The alveolar portion of the bones externally has the same form as in the Camel, and 

 the infra-orbital foramen holds the same relative position, being situated above the 

 last premolar. 



The molar series form a closed row of six, independent of a caniniform premolar 

 which may have existed in the jaw. 



The true molars, so far as can be judged from their much mutilated condition in 

 the fossil, appear to have had the same constitution and form as in the Camel and 

 Lama. 



