Lee — Lower- Paleozoic Pocks of Central New Mexico. 185 



east of Red Cabin and also north of Rincon, may be correlated 

 more or less definitely with the Maquoketa shale and this with 

 the upper Richmond of Ohio and Indiana." 



No fossils were found in the black shale (No. 2) of the Red 

 Cabin section, and it may be Devonian as stated by Gordon 

 and Graton.* It is apparently this shale that these writers 

 have in mind when they state that the Devonian is represented 

 in the Caballos Mountains, although it does not appear from 

 their descriptions that fossils were found or other evidence of 

 age except stratigraphic position obtained. The overlying 

 Permsylvaniaii limestone rests in some places upon this shale, 

 in other places upon the Richmond chert, as shown in the Red 

 Cabin section, and in still other places upon the chert overlying 

 the Richmond, as in the Shandon section. No rocks of Mis- 

 sissippian age were found, but their occurrence a few miles to 

 the west suggests that the Mississippian limestones once 

 extended over this region and that they, together with the 

 greater part of the Devonian, were removed by erosion previ- 

 ous to the deposition of the Pennsylvanian sediments. 



A small exposure of cherty limestone was found beneath 

 the Pennsylvania!! limestone in the northern slope of the 

 Robledo Hills about 15 miles south of Rincon. In this chert 

 I found the following fossils : 



Lophospira, two small undet. species. 

 Lophospira, ? larger species. 

 Trochus f sp. undet. 

 JBucania? sp. undet. 

 Trochone?na, sp. undet. 

 JEoiomaria, sp. undet. 



Pen tarn eroid shell agreeing with Sieberella, except 

 that it has no fold nor sinus. 



ITlrich regards these as constituting a part of the Richmond 

 fauna just described, but states that they are clearly distinct 

 from other Richmond faunas so far as known from the west 

 and southwest. His statement that more perfect fossils may 

 prove that the fauna is Silurian finds support in the occur- 

 rence of Silurian rocks in the Franklin Mountains 35 miles to 

 the south.f A thickness of only a few feet of the rocks is 

 exposed in the Robledo Hills and their relations to other for- 

 mations could not be determined. 



A summary of the foregoing statements regarding the lower 

 Paleozoic rocks of central New Mexico may be given as fol- 

 lows : (1) Rocks of upper Cambrian age about 100 feet thick 

 rest upon an eroded plane of granite. (2) Rocks of early 



*Ibid., p. 391. 



f Kichardson, G. B., U. S. Geol. Survey, El Paso Folio. 



Am. Jour. Sci. — Fourth Series, Vol. XXVI, No. 153.— September, 1908. 

 14 



