20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I23 



been removed posterior to Mi on the labial side. The incisor is 

 rounded ventrally, with the transverse width approximately one-half 

 of the dorsoventral height. 



P4 is rectangular in shape and approximately one-half as wide as 

 Ml. The metaconid is much larger than the protoconid. The proto- 

 conid is slightly posterior to the metaconid. The median sides of the 

 two cusps join and will wear to a distinct anterocrest. They are 

 higher than the entoconid and hypoconid, and are separated from 

 them by a broad, deep valley. There is no mesoconid or mesostylid 

 present, nor are these present on Mi— M3. The entoconid is distinct 

 and well separated from the hypoconid by a narrow valley. The ento- 

 conid is as large as the metaconid. The hypoconulid is distinct, and 

 as large as the protoconid. Mi is smaller than M2, which is the 

 largest tooth. Mi is nearly square in outline, being slightly longer 

 than v/ide. Mo is square in outline. The cusps are distinctly de- 

 veloped in these two molars, the protoconid and metaconid being 

 separated by a narrow, shallow valley. The hypoconid and ento- 

 conid are more distinctly separated. The anterior cingulum is con- 

 fined to the anterior face of the protoconid. The lingual cusps of 

 P4-M3 are higher than the labial cusps, except the entoconid of 

 M3, which is the same height as the hypoconid. The metaconid and 

 protoconid of Mi and M2 would have worn to form a pronounced 

 anterocrest. A distinct hypoconulid is present on Mi and M2. M3 is 

 rounded posteriorly and is the size of Mi. The anterior cingulum is 

 not so pronounced as that of Mi and Mo. The valley separating the 

 protoconid and metaconid of M3 is deeper than on Mi and M2. This 

 valley is approximately the same depth as the lingual side of the trans- 

 verse valley on M3. The hypoconid is large while the hypoconulid 

 is reduced and becomes a part of the posterior cingulum. M3 would 

 never develop, with wear, the pronounced anterocrest that would be 

 developed on P4, Mi, and M2. 



The teeth of the left ramus are like those of the right. The pos- 

 terior part of the left ramus is missing. Both lower jaws were tightly 

 compressed in a small nodule of matrix with the fragmentary maxil- 

 lary. Parts of the upper incisors are present. They are narrow 

 transversely, and the curvature is circular in outline. 



The paratype, U.S.N.M. No. 20139, is a fragmentary left 

 ramus of a young individual. The anteroposterior length of 

 P4-M3 is 5.1 mm. The cusps of P4 and the protoconid of Mi show 

 evidence of some occlusal wear. Owing to the lack of wear the valley 

 separating the protoconid and metaconid of Mi and M2 is much 

 deeper than in the holotype and emphasizes the distinctness of these 



