12 PROCEEDINGS OF THE NATIONAL MUSEUM vol.91 



Table 1. — Measurements (in millimeters) of lower teeth of Aphronorus simpsoni 



Measurement 



Anteroposterior diameter. 

 Transverse diameter 



P4 



3.8 

 2.0 



Ml 



3.0 

 2. 1 



M, 



3.0 

 2.2? 



M3 



3.2 

 2.2 



Pantolestid (a), genas and species undetermined 



A maxillary portion (fig. 5), No. 16184, with M^ and M^, represents 

 a pantolestid insectivore near Bessoecefor. The teeth are relatively 

 wide transversely, M^ being about .one-fourth wider than in Bes- 

 soecetor thovuoni. Anteroposteriorly the tooth is about the game, or 

 possibly as much as a sixth greater than in B, thomsoni. The hypo- 

 cone is markedly lingual in position and the anteroexternal angle, 

 though partially broken away, is seen to be much heavier than in M^ 

 of the Scarritt Quarry form. The anterior wall of M^ shows a 

 somewhat heavier cingulum and the posterior wall does not show 

 so acute a notch adjacent to the metaconule, M^, 

 though poorly preserved, appears to be anteropos- 

 teriorly compressed. Both teeth are much more re- 

 duced anteroposteriorly than in Aphronorus^ and 

 the external styles are directed more as in Bessoe- 

 cetor. Moreover, the teeth are nuich smaller than in 

 Palaeosirvopa senior^ also recorded from the Scarritt 

 Quarry in the Crazy Mountain field of Montana. 



A lower jaw portion, No. 16219, with M3 pre- 

 served may belong to this form. M3 has the trigonid 

 structure much as in Bessoecetor^ or even Aphro- 

 7wrus, but the talonid is more reduced than in B. 

 diluouli, somewhat as in B. thomsoni. However, its 

 size is such as to suggest a relationship to the form 

 represented by the upper molars described above, 

 and the reduced talonid is quite in accord with the anteroposterior 

 reduction of M^ in No. 16184. 



The anteroposterior and greatest transverse diameters of M-, N.o. 

 16184, are 2.5 (approximately) and 4.9 mm., respectively; of M3, No. 

 16219, 2.7 and 2.0 mm. 



Pantolestid (b), genus and species undetermined 



A single upper molar. No. 15791, provisionally referred to Aphro- 

 norus simpsoni, seems on further consideration to represent not 

 Aphronorus but a pantolestid type closer to Bessoecetor. The tooth 

 is about a third smaller than the M- in the form herein described as 

 pantolestid (a), hence somewhat smaller than either of the first 



Figure 5. — Panto- 

 lestid (a), gen. 

 and sp. undet. : 

 Maxillary por- 

 tion with M- and 

 M3 (U. S. N. M. 

 No. 16184), oc- 

 clusal view, X 4, 

 Dragon Paleo- 

 cene, Utah. 



