162 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 



The dental formula is also most completely known in Carjwlestes 

 duhius, in which it is tjxIj^^ ^s in Paromomys. The incisor is en- 

 larged but does not extend beneath P4, also as in Paromomys, but the 

 canine is more reduced. In both Carpolestes and Carpodaptes P2-3 

 are reduced to 1 -rooted vestiges with buttonlike crowns. 



Noting these divergent specializations, bat also the strong hint of 

 tarsioidlike upper molars, in the most specialized genus of the phylum 

 in characters not known in Elphidotarsius, we may expect the latter 

 to cast more light on affinities as far as its more scanty remains go. 

 P4 in this genus could easily be derived from one like that of, say, 

 Palaechthon, but it is already too specialized, and its structural ancestor 

 must have been too generalized, to cast any real light on affinities. 

 Ml also shows what may be taken as the beginning of a narrowly 

 phyletic specialization in its elongate trigonid. Otherwise it is much 

 like that of many tarsioids but of too generalized a heritage to give 

 decisive evidence. M2-3 are almost exactly like those of Pronothodedes , 

 so much so that were this form known from those teeth alone it would 

 have to be defined as a species of Pronothodectes. They also resemble 

 to a marked degree those of Eocene primates of other groups, such 

 as Wmomys vespertinus and, in less degree, Pelycodus. As far as I know 

 they do not so closely resemble any genus not now considered as 

 primate. The characters that are distinctive from the most generalized 

 tuberculosectorial pattern and that are not clearly habitus characters 

 or otherwise neomorphs of this very restricted phylum all appear to 

 me to be definitely primate. To tliis extent I cannot agree with Jepsen 

 (1930a, p. 523 — he was, however, dealing only with the much more 

 aberrant terminal genus Carpolestes and had not recognized the 

 relationship to Elphidotarsius) that "it is possible to select suites of 

 characters which, taken by themselves, would place Carpolestes in any 

 one of several orders." I do, of course, recognize that a really defini- 

 tive determination of affinities is in such cases practically impossible 

 from teeth alone, but since teeth are, in fact, all we have I see no 

 useful alternative to classifying them at least tentatively as belonging 

 to the group they most resemble, that is, to the Primates. 



The family in wliich these related, aberrant animals are placed was 

 defined and discussed in revising the Tift'any fauna (Simpson, 1935c). 



Genus ELPHIDOTARSIUS Gidley 



Elphidotarsius Gidley, 1923, p. 10. 



Type. — E. florencae Gidley. 



Distribution. — Middle Paleocene, Fort Union, Montana. 

 Diagnosis. — Three lower molars and at least one premolar, dental 

 formula otherwise unknown. P4 enlarged, equaling or exceeding Mi in 



6' Jepsen writes 1.0.4.3. It is, of course, Impossible to say which is correct, but the form I give seems to 

 me slightly more probable, and it facilitates comparison by being consistent with the other formulae hero 

 used. 



