52 BULLETIN 169, UNITED STATES NATIOX.AL MUSEUM 



CORRELATION OP MAMMALIAN FAUNAS 



Data are not at hand for any exact correlation of the No. 1 beds. 

 Of then- mammals IPtilodus sinclairi, identified here with some prob- 

 ability, is a No. 2 species. Claenodon is typically a Middle Paleocene 

 genus, ranging in this field into the Upper Paleocene. Chriacus is a 

 very long-lived genus. Lower Paleocene to Lower Eocene, and is here 

 rather dubious but apparently of more progressive aspect than it& 

 Lower Paleocene allies. Alimotricentes is otherwise known only in the 

 Middle Paleocene of tliis field, and M. angustidens (which, however, 

 is known only from the highest No. 1 beds) ranges to the top of the 

 No. 2. Tetradaenodon is typically Middle Paleocene, perhaps ranging 

 into earliest Upper Paleocene in this field, and the species may be the 

 same as in the No. 2. As identified by Russell (personal communica- 

 tion), invertebrates from immediately below the No. 1 beds, or perhaps 

 in their base, are definitely of Paleocene aspect, and most of his com- 

 parisons are closely with Middle to Upper Paleocene forms. On the 

 whole the scanty evidence favors reference of the No. 1 beds to the 

 Middle Paleocene, and none of it definitely suggests or warrants 

 reference to the Lower Paleocene. The physical stratigraphic evi- 

 dence, while even less decisive, is also consistent with belief that the 

 No. 1 beds are not markedly different from the No. 2 in age. Nothing 

 suggests or justifies correlation with the Puerco. 



As already shown, the fauna of the No. 2 beds is a unit as far as 

 correlation is concerned. From his first discovery (Locs. 5 and 6), 

 Douglass (1902) already recognized equivalence to the Torrejon. 

 Matthew (1914) accepted this fauna as of the same age as that of 

 the Torrejon.^* Gidley (1909, p. 616, footnote, apparently not else- 

 where explicitly stated, but liis definitive opinion) considered it "about 

 equivalent to ... or perhaps somewhat older than the Torrejon." 

 The detailed evidence of the mammalian fauna is as follows: 



Ptilodus: A Middle Paleocene genus, P. montanus very near P. mediaevus of the 



Torrejon. 

 Eciypodus 1 [TypicaUy Upper Paleocene genera, but species here quite distinc- 

 Parectypodus]' { tive and generic assignments not certain. 

 Eucosmodon: Forms indistinguishable generically on the basis of similar material 



range through the Paleocene. 

 Gelastops: Probably allied to, but distinct from, Didelphodus of the Lower Eocene. 



Probably allied to but less specialized than Acmeodon of the Torrejon. 

 Prodiacodon: Middle Paleocene genus, identification here not certain and species 



highly distinctive. 

 Leptacodon: Genus otherwise Upper Paleocene, species distinctive. 

 Myrmecohoides: Unknown elsewhere, no value in close correlation. 

 Stilpnodon: This genus and its family too imperfectly known for close comparisons. 

 Bessoecetor: Otherwise known only in the No. 3 beds in this field, allied to the 



typically Lower Eocene Palaeosinopa, but more primitive. 



1* Uis correlation chart, fig. 2, seems to correlate it with the Puerco, but his text shows that this was not 

 intended. 



