. Bulletin. Natural history; Natuurlijke historie. EARLY CENOZOIC MAMMALIAN FAUNAS, FA YUM 67 Isolated right lower molars from Quarry G (YPM 18205) and Quarry E (YPM 18194) are slightly above the upper limit of size of material referred to Ph. andrewsi (compare Tables 1 and 3), and slightly below the lower limits of M. schauhi (Tables 3 and 9). They could be considered simply as aberrant indi- viduals of either form. On the other hand, the presence of a strong posterior arm of the protoconid directed toward the base of the metaconid and bearing a pro- nounced protospur (fig. 13 A) is diagnosti
. Bulletin. Natural history; Natuurlijke historie. EARLY CENOZOIC MAMMALIAN FAUNAS, FA YUM 67 Isolated right lower molars from Quarry G (YPM 18205) and Quarry E (YPM 18194) are slightly above the upper limit of size of material referred to Ph. andrewsi (compare Tables 1 and 3), and slightly below the lower limits of M. schauhi (Tables 3 and 9). They could be considered simply as aberrant indi- viduals of either form. On the other hand, the presence of a strong posterior arm of the protoconid directed toward the base of the metaconid and bearing a pro- nounced protospur (fig. 13 A) is diagnostic of Metaphiomys. However, the poste- rior arm of the protoconid reaches the metaconid at a very low level and there is a swelling of the ectolophid representing a mesoconid; both are primitive features. Analysis of these specimens, using the t test (Simpson, Roe and Lewontin, 1960,. FIGURE 13. Isolated teeth of Phiomys or Metaphiomys sp. indet., X 10. A. Right Ml, YPM 18205. B. Left dP^ YPM 18089. C. Left M\?), YPM 18089. D. Right M=(?), YPM 18089, anterior end to the right. p. 182) shows that they cannot be separated either from Ph. andrewsi or from M. schaubi. The probabilities that the measurements are not distinct from those of Ph. andrewsi range from about .005 for the hypolophid width to about .08 for the length; compared with M. schaubi the p values range from something less than .01 to something over .01. Three isolated upper cheek teeth from Quarry G (YPM 18089, fig. 13, B-D) are of the correct size to belong with these two lower molars, and are distinctly more primitive than are the upper molars of M. schaubi. The mesoloph is short (fig. 13 C), multiple (fig. 13 D), or absent (fig. 13 B). The first of these suggests M. schaubi; the second. Ph. andrewsi; and the third seems to be unique. The anterior cingulum extends to the lingual as well as to the buccal margin of the teeth, a character not found in any of the other teeth in the collections. Not enough specimens of
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