712 JAMES H. GARDNER 



and Lower Beds, but this scarcely gives an adequate idea of the occurrence of 

 the fossils, for the reason that it is only the extreme upper and lower strata that 

 are productive; the great intermediate part we found to be singularly barren. 



The lower fossil-bearing strata occur in two layers, the lowermost of which 

 lies with ten or fifteen feet of the base of the formation. This is succeeded after 

 an interval of about thirty feet by a second stratum in which fossils are found, 

 and this appeared to be by far the richer of the two. Both of these strata 

 are of red clay, and at no place did we find them more than a few feet in 

 thickness. 



The lower horizon we found exposed in two places, viz.: the head of the 

 Coal Creek or Pina Verta Canon, and some of the upper tributaries of the Chaco 

 Canon. It is especially and sharply distinguished by the occurrence of the 

 remains of Polymastodon, which appear to be entirely absent from the upper 

 horizon. 



Fossils are much more abundant in the upper strata, and wherever a good 

 exposure was found their occurrence could be more confidently looked for. The 

 genera Chirox and Pantolambda appear to belong exclusively to the upper beds. 

 Owing to the widely separated localities and the general scarcity of fossils, it is 

 at present impossible to say whether it is one or several layers that produce the 

 fossils from these upper beds. It is my opinion, however, that there are several 

 layers, and that their vertical range is somewhat greater than that of the lower 

 horizon. The principal localities of the upper strata are as follows: head of 

 Canon Gallego, Canon Blanco, Canon Escavada, and head of Canon Chaco. 



. It will be noted that near the beginning of the above quotation 

 Wortman states that the Puerco beds "as far as can be observed lie 

 conformably upon the Laramie." This statement is somewhat 

 qualified perhaps, due to the uncertainty which necessarily arises 

 from a study of formation contacts in undisturbed, unconsolidated 

 deposits; it is especially difficult to recognize an unconformity in 

 badland topography in the absence of abundant fossils and especially 

 so without detailed, continuous mapping. 



Wortman states that the two lower fossil zones lying within fifty 

 feet of the base of the Puerco are characterized by the remains of 

 Polymastodon, whereas the fossil zone near the top contains Chirox 

 and Pantolambda which do not occur in the lower beds. In fact the 

 faunas of the upper and lower beds of the original Puerco were found 

 to be entirely distinct, which later led to the substitution of the name 

 Torrejon formation for the upper strata and the restriction of the 

 name Puerco formation to the lower beds. 



