412 MAMMALIAN ANATOMY 



The upper molar (Fig. 328) is a very small, two-rooted tooth, 

 placed transversly to the alveolar border, close behind and in contact 

 with the posterior end of the sectorial. 



The transversely oval crown differs from the crowns of all the 

 other teeth in presenting a small tubercular grinding surface in place 

 of the sharp triangular cusp. The outer end of the crown is wider 

 and more prominent than the inner end. The posterior border 

 exhibits near the middle an inconspicuous tubercle, from which a ridge 

 curves forward and outward along the anterior border to an outer cusp* 

 Behind the ridge is a crescentic depression. The inner slightly tuber- 

 cular end of the crown is separated from the middle tubercle by a 



FIG. 329. 



.Middle Cusp. ^ Middle Cusp. 



Outer Cusp. f^jj- Inner Cusp. p"Jf_ Outer Cusp. 



-Neck. 



Fang. --i I Fang. 



ANTERIOR POSTERIOR OUTER 



ASPECT. ASPECT. ASPECT. 



RIGHT FIRST LOWER INCISOR TOOTH. 



shallow groove, which notches the posterior border and slopes upward 

 at the anterior border. This may be regarded as the condition of the 

 crown when the tooth is fully developed and unworn ; often, however, 

 the tooth is rudimentary or the peculiar features of the crown have 

 been worn away. The fangs are variable in size ; the outer appears 

 to be constantly the larger. The anterior edge of the crown wears 

 against the posterior surface of the lower molar (Fig. 337). 



FIG. 330. 



f Middle Cunp.^ Middle Cusp. 



Outer Cusp.C*'"*k-I ne >' Cu&p.-f^fj Outer Cusp._ 



Fang. 



ANTERIOR POSTERIOR OTTER 



ASPECT. ASPECT. ASPECT. 



RIGHT SECOND LOWER INCISOR TOOTH 



The lower incisors closely resemble the corresponding upper teeth ; 

 they are smaller, however, and the posterior surface of the crown is 

 not crossed by the transverse groove. 



