20 GIRTY 



fornia Carboniferous section, which has stood for a long time 

 more or less solitary and unique among its kind in America, 

 because of the singularity of its faunas. Accordingly, Tscher- 

 nyschew correlates syntactically the Omphalotrochiis zone of 

 eastern Russia with the McCloud limestone of California. But 

 the genus Om^halotrochiis characterizes certain horizons over 

 wide areas in Nevada, and by reason of a somewhat similar 

 resemblance the Hueco formation of Western Texas may like- 

 wise be tentatively referred to the Om^halotrochus zone, for 

 one horizon abounds in Ouiphalotrochtis, several species of 

 which occur. 



The fossils of the Hueco, Delaware Mountain, and Capitan 

 formations, as would be expected from their combined thick- 

 ness, represent a sequence of related faunas, rather than a 

 single uniform one. Whatever is here said about these faunas 

 is qualified by the fact, on the one hand, that they are 3'et, as 

 to detailed study, largely unworked, while, on the other, my 

 acquaintance with the Uralian series is only such as literature 

 affords. Nevertheless, I seem to see in the Texas faunas re- 

 semblances to the Sptri/er maf'coui, Oni^halotrocJuts zvhitneyi, 

 ProducUis cor a, and Schivagerma zones as their fossils are 

 represented by Tschernyschew. All three of the lower faunas 

 are probably represented by the Hueco formation, while the 

 fauna of the Capitan limestone is in some respects strikingl}^ 

 similar to that of the Schzvagcrina zone. Sundry types which 

 seem to abound in the Russian beds, however, are thus far un- 

 known in Texas, while in some cases the association of species 

 is different, indicating that certain forms appeared later in one 

 area than in the other, or had a different range. A fauna 

 which I collected northeast of Hueco Tanks, on the brow of 

 the escarpment overlooking the valley, especially suggests the 

 S-pirifer marcoui zone. Omphalotrochtis also occurs at this 

 point, but it is much more abundant at a somewhat higher hori- 

 zon, where it is associated with a varied gastropod fauna. A 

 considerable thickness of rocks succeeds, with varying faunas 

 more or less closely related to those below, and it is safe to sa}^ 

 that 3,000 feet of sediments are measured above these before 

 the top of the Capitan limestone is reached, the faunas of which 



