414 



MAMMALIAN ANATOMY 



The crown is strongly curved backward, and presents an anterior 

 outer surface, which is convex and ridged ; a posterior outer surface, 

 which is twisted, concave from above downward, and slightly convex 

 from side to side ; and an inner surface, which is slightly concave from 

 above downward, and almost flat from before backward. The emargi- 

 nate posterior inner border is sharp, and shears against the anterior 

 border of the upper canine. 



FIG. 333. 



Anterior Basal Cusp. 

 Cingulum. 



Anterior Fang. 



-Principal Cusp.- 



Posterior Basal Cusp' 

 Talon. 



Posterior Fang. 



Anterior Basal Cusp. 



Anterior Fang. 



INNER ASPECT. 



Principal Cusp. 



Talon. 

 Inner Side. 



OUTER ASPECT. 



Outer Side. 

 Posterior Basal Cusp. 



Posterior Fang. 

 Anterior Fang. 



POSTERIOR ASPECT. 

 RIGHT FIRST LOWER PREMOLAR TOOTH. 



The first lower premolar (Fig. 333) is separated from the canine 

 by a long diastema, but is close to the second premolar. It is a much 

 larger tooth than the very small first upper premolar, and closely 

 resembles the second lower premolar ; it is smaller, however, and the 

 anterior cusp of the cingulum is less prominent, or may be absent ; 

 hence the anterior fang is more slender. It is not unlike a small 

 second upper premolar ; its posterior fang, however, is not prismatic. 

 The lower jaw is so much narrower than the upper jaw at this point 

 that the first lower premolar cannot strike the upper teeth. 



The second lower premolar (Fig. 334) has been already described 

 (page 405). Its prominent anterior cusp and its subequal fangs dis- 

 tinguish it from the corresponding upper premolar. The anterior 

 part of the outer surface of its crown wears against the posterior part 

 of the inner surface of the crown of the upper premolar (Fig. 337). 



