62 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



ties have been very closely examined and fragments as small as the 

 smallest isolated insectivore or primate teeth recovered, so that the 

 almost total absence of those groups must really result from their 

 great raritj^ here. Furthermore, the arctocyonids are really much 

 more abundant at these localities, for not only the relative but also 

 the absolute number of specimens is greater for these localities than 

 for the Gidley and Silberling Quarries, despite the much larger col- 

 lections from the latter. This "surface" fauna, 90 percent carnivores 

 and ungulates, is of more normal type, in comparison with Tertiary 

 faunas generall}^, than are the quarry faunas. Its members average 

 larger than do those of the quarry faunas, and they are probably 

 terrestrial for the most part. This appears to be a normal flood-plain 

 facies, rather closely analogous to that of the Torrejon.^^ Its most 

 marked peculiarit}'' is the higher percentage of carnivores than of 

 herbivores, a condition for which no probable explanation is seen. 



Even at the surface localities there is a surprisingly low percentage of 

 animals really of large size for the Paleocene. The phenacodonts are 

 of average size for that group, but the periptychids (all Anisonchus) 

 are moderate in size, much smaller than the contemporaneous Peripiy- 

 chus, and most of the carnivores are also of middle size, wdth Deutero- 

 gonodon very rare and other large carnivores absent, although they 

 were common at this time in the Torre j on. 



This rarity of large animals is still more obvious in the quarries. 

 Phenacodonts and pantolambdids are relatively very rare, Claenodon is 

 uncommon, and other large mammals do not occur. The most abun- 

 dant species, Ptilodus montanus, IP. sindairi, Leptacodon ladae, Apliro- 

 norus fraudator, Paromomys maturus, Palaechthon alticuspis, Meta- 

 chriacus punitor, Didymicfis microlestes, and Ellipsodon aguilonius, are 

 moderate to minute in size. 



In food habits the multituberculates were rodentlike, the insecti- 

 vores doubtless insectivorous (as the word is usually used, not signify- 

 ing a diet composed of insects), the primates probably mainly or ex- 

 clusively frugivorous, the creodonts in part omnivorous (Claenodon), 

 omnivorous-carnivorous (other arctocyonids), and predaceous-carniv- 

 orous (miacids), and the condylarths probably browsing, perhaps in 

 part frugivorous, or even partly insectivorous for the smallest forms. 

 The known fauna apparently consumed every type of food known to 

 have been present in the area, with the possible exception of the 

 mollusks. 



The skeletal structure is too poorly known for any of these animals 

 to give much dii-ect insight into their locomotion or general habitus. 

 By analogy and comparison with allied species and genera, the multi- 

 tuberculates and insectivores were unguiculate and probably in good 



" Correlation of faunal types and collecting methods is real but indirect. Flood-plain deposition and 

 facies would not normally result in concentration of fossils sufficient to permit profitable quarrying. 



