NO. 7 EARLY CENOZOIC VERTEBRATES — FRIES ET AL. I9 



that the hypocone has shifted slightly toward the center of the tooth 

 and gives a slightly rounded appearance to posterolingual corner of 

 the tooth. The accessory conule at the anteromedian edge of the 

 hypocone is larger than that of M^ and extends well into the trans- 

 verse valley filling the posterior part of this valley between the median 

 bases of the metacone and hypocone. In wear the anterocrest and 

 posterocrest would join on the lingual side first and a broad U-shaped 

 pattern would exist on M^ much longer during occlusal wear than on 

 P^ or M^ owing to the development of the accessory conule on the 

 hypocone. 



M^ is reduced, posteriorly rounded, and smaller than M^ and M-. 

 It is slightly larger than P*. The protocone is twice as large as either 

 the paracone or hypocone. The metacone is greatly reduced. The 

 paracone joins the protocone by a narrow protoloph. This condition 

 did not exist in P^-M^, owing to the large development of the para- 

 cone and protocone. In these teeth the median sides of the paracone 

 and protocone join each other. The anterior cingulum of M^ is well 

 developed. It extends from the anterolabial edge of the paracone to 

 the anteromedian edge of the protocone. A deep valley, deeper than 

 on the other teeth, is present between the cinglum and the anterocrest. 

 The metacone is a low small cusp that closes the labial reentrant 

 valley. The valley narrows rapidly at the midline of the tooth to 

 end abruptly at the base of the large protocone. The lingual part of 

 the transverse valley is closed by the large accessory conule that is 

 developed on the hypocone. Posterior to the small metacone and 

 forming the posteromedian border of the tooth is a cusp larger than 

 the metacone. This cusp is continuous with the metacone. Its base 

 joins the base of the hypocone. It is not so high as the hypocone. 

 The posterior cingulum, which is very short, connects the occlusal 

 surface of the accessory cusp (apparently developed from the cingu- 

 lum) with the occlusal surface of the hypocone. 



The following description is taken from the right lower jaw of 

 the holotype. The diastema between the incisor and P4 is short, being 

 2.6 mm. The ramus is noticeably deeper below P4 than below M3. 

 There is no pit, depression, or broad shelf between M3 and the 

 ascending ramus. The dental foramen is situated posteriorly, 4.6 mm. 

 from M3. It is a narrow, elongated slit. The ventral surface of the 

 angular process forms a distinct shelf. The mental foramen is small 

 and is anterior and ventral to P4. The masseteric ridge is not pro- 

 nounced. The masseteric fossa extends anteriorly as far as the middle 

 of Ml. Owing to the fragile condition of the jaw, the matrix has not 



