130 GEORGE H. GIRTY 



differentiated than those east of the Rocky Mountains. At least three 

 well-marked facies can be recognized. The oldest of these is found 

 in the limestones whose occurrence has already been mentioned, resting 

 directly upon Lower Mississippian limestones of similar character 

 in Arizona and probably in Utah. This fauna is succeeded by one 

 which is best considered from its development in the Transpecos region 

 of Texas, because it is there more highly developed, more favorably 

 studied, and more determinable in its stratigraphic relations with 

 higher beds. It occurs in the Hueco formation which is 5,000 feet 

 thick, and is practically calcareous throughout. As has already been 

 noted, the Hueco formation by overlap rests upon the pre-Carbonif- 

 erous in this region. The Mississippian faunas, together with the 

 earlier Pennsylvanian ones, appear to be absent. The Hueconian 

 fauna is widely distributed over the West, ranging indeed into Alaska, 

 while it is even recognizable in Asia and eastern Europe. Most of 

 the occurrences of Carboniferous in the West can be referred to this 

 series, although some or them present more or less distinctive facies. 

 The more important of the facies provisionally referred to the Huecon- 

 ian are these: that of the Aubrey group of Arizona, rather widely 

 distributed; that of the phosphate beds of the Preuss formation, local 

 in Utah, Idaho, and Wyoming; the Spirijerina pulchra fauna with a 

 considerable distribution in Idaho, Wyoming, Utah, and Arizona; 

 the fauna of the McCloud limestone of California probably extending 

 into Nevada; and that of the Nosoni formation of California (in 

 part the "McCloud shale"), apparently recognizable to the eastward 

 and to the North and West, even into Alaska. 



In the Transpecos the beds of the Hueco formation are succeeded 

 by those of the Guadalupe Mountains. The contact between the 

 Hueco formation and the Guadalupian series is obscured by faulting 

 and by desert deposits, but it is assumed that the interval between 

 the highest known beds of the one and lowest known beds of the other 

 is not a long one and that no unconformity exists between them. The 

 Guadalupian includes two formations, the Delaware Mountain forma- 

 tion and the Capitan limestone. The Delaware Mountain formation 

 consists of sandstones and limestones, largely arenaceous to the North 

 and largely calcareous to the South. The Capitan consists of whitish 

 limestones and dolomites. Thus constituted the Guadalupian series 



