PREVIOUS INVESTIGATIONS 579 



Cretaceous age, but Lesquereux (49) tried to strengtlieu liis reference of 

 the coal beds to the Tertiary by the evidence of the fossil plants. 



In 1876 the delayed publication (44) of Xewberry's account of liis 

 expedition with Macomb in 1859 appeared, and with it Meek's (4:5) de- 

 scription of the fossil shells collected by Newberry during that expedi- 

 tion. The coal beds of the Cerrillos field and those of the San Juan 

 Basin are referred to "Middle Cretaceous," which, according to Xew- 

 berry's classification, make them equivalent in time to the Niobrara. 

 Cope (45) followed a year later with a paper, in which he referred these 

 same coal beds, west of Nacimiento and (Jallinas Mountains, to C-retace- 

 ous number 3, which, as just explained, is equivalent to the upper part 

 of Newberry's "Middle Cretaceous." About a year hiter a striking ex- 

 ample of the difference of opinion existing between the authorities of 

 that time appeared when Lesquereux (49) included in his Tertiary flora 

 plants from the coal measures of the Cerrillos field which Newberry 

 (44) had previously referred to "Middle Cretaceous." 



In 1877 Hayden's Atlas of Colorado was published and doubtless had 

 great influence on such investigations as were later made in New Mexico. 

 The mapping was extended southward over the area near Monero, de- 

 scribed in this paper. By inspection it appears that the Colorado for- 

 mation of this Atlas includes the shale both above and below the main 

 coal beds which Newberry and Cope had referred to Cretaceous number 

 3. These are the coal beds which Schrader (100) later mapped as Mesa- 

 verde. The Atlas map shows the occurrence of a considerable develop- 

 ment of so-called Fox Hills rocks in this region overlain by Wasatch. It 

 is not clear what this "Fox Hills" is intended to represent, unless it be 

 the very thin "Laramie" Avhich occurs at Dulce and the massive sand- 

 stones of the post-"Laramie" formation, which is now known to lie un- 

 conformably on the "Laramie" in the vicinity of Dulce. 



In 1878 and 1879 J. J. Stevenson examined the Cerrillos coal field and 

 published (51) a preliminary account, in which he refers the coal-bearing 

 rocks to the Laramie. At a time when such wide differences of opinion 

 existed, as is indicated above, it would seem especially difficult to find 

 the truth. Furthermore, Stevenson had worked east of the mountains 

 in the Canyon City field and in the Eaton Mesa region in beds which, 

 by common consent, were called Laramie. Although some geologists had 

 referred the Cerrillos coal beds to Cretaceous number 3 (Niobrara) and 

 others had regarded them as younger than this, but still somewhat 

 older than those of the Eaton Mesa, Canyon City, and Denver fields, 

 there seems to have been a general assumption at this time that the coal 



