Cope.] 4:J4: [-Sept. 17, 



The dimensions of the superior molars increase to the penultimate, 

 while the external and posterior sides of the last molar are contracted, re- 

 ducing its size. The external faces of the external Vs of the true molars 

 are considerably impressed ; those of the premolars are nearly flat. 



The second premolar is two-rooted, and has a compressed crown, with- 

 out either heel or cingulum, except a thickening of the posterior base. 

 The base of the crown is triangular. The external plate of the third pre- 

 molar is simple, and is connected with the internal cusp by a cingulum 

 on the posterior base of the crown. The crown is transverse, and the 

 inner tubercle rather small. The fourth premolar is much larger than the 

 third. Its external plate is divided into two apices, which are not im- 

 pressed. Their external faces are separated by a faint ridge, and are 

 divided medially by a faint ridge. The anterior external angle is rather 

 prominent. The anterior and a posterior cingulum extend to and round 

 the inner base of the interior tubercle. Within the anterior external apex, 

 is a well developed intermediate crest parallel to it ; and there is a corres- 

 ponding crest within the posterior external apex. This one turns inwards 

 at its posterior extremity, which is on the posterior cingulum. 



The anterior angle or horn of each external crescent of the true molars is 

 very prominent. They are sections of short vertical ridges, which unite 

 near the base of the crown, giving abruptness to the impression of the ex- 

 ternal surface of the anterior lobe. The middle of each face has a faint 

 median ridge. The two molars have an anterior basal cingulum, but no 

 posterior or internal, excepting a trace between the bases of the internal 

 lobes. The anterior intermediate crescent is quite parallel with the ex- 

 ternal ; the anterior internal tubercle has a slightly V-shaped section. The 

 posterior inner tubercle is quite confluent with an oblique intermediate 

 crest, as in M. chamense. In the last true molar, as there is only one in- 

 ternal tubercle, this crest is short, terminating at the posterior border. 

 The last true molar is like the last premolar, except in its two impressed 

 external crescents. 



A fragment of the right branch of the lower jaw supports two molars, 

 and the alveoli of two others, all of which have two roots. These teeth 

 are the four premolars, although the last one has the form of the first true 

 molar. Should my surmise be correct, then the third premolar has nearly 

 the same form and structure as the fourth. The anterior horn of its ante- 

 rior V is not produced quite so far inwards as in the fourth tooth. At the 

 point of i unction of the adjacent horns of the Vs there is a slight antero- 

 posterior extension, forming a median buttress of the inner side of the 

 crown as in AncliitJierium. The posterior horn of the posterior V is also 

 incurved, as in that genus. The angles of the Vs of the inferior molars 

 are rounded. 



The surfaces of the enamel of the teeth of both jaws is smooth. 

 Measurements. M. 



Length of superior molars, less P-m. I 046 



' ' of true molar series 028 



" of base of P-m. II .005 



