W. P. Jenney—Notes on the Geology of Western Tecas. 27. 
the range has attained its present elevation. Owing to the crys- 
talline character of the limestone, nearly all traces of life are 
destroyed; but a few fragments of imperfect shells resembling a 
Pentameras were found near the contact with the conglomerate, 
so that the lower portion of this bed may be of Niagara age: 
but the resemblance of the limestone of the upper part of this 
ridge to that of Carboniferous age in the parallel range of the 
Hueco Mountains leads me to think that, on a more extensive 
examination, it will be found to be equivalent to it. 
Dr. G. G. Shumard seems to have examined this same range, 
but at a point farther north. He mentions the occurrence of a 
limestone of Trenton and Hudson age succeeded by the Car- 
boniferous. (Dana, Manual of Geology, p. 245. 
About two miles west of this locality, on the banks of the Rio 
the Silurian and Carboniferous limestones in the Organ, Hueco 
and Guadaloupe Mountains, no strata containing any Devonian 
forms of life were found. It appears, therefore, that the greater 
Portion of the Upper Silurian and the whole of the Devonian 
periods are unrepresented in the rocks of Western Texas. __ 
An immense avec oat of Carboniferous strata occurs In 
the Sacramento and Guadaloupe Mountains, between the Pécos 
and Rio Grande; at Guadaloupe Pass, about 800 feet of sand- 
stone underlie a precipice nearly 600 feet high of Carboniferous 
limestone, above which the peaks of the mountain rise to pe 
haps an equal height. 
At the banks of Los Cornudos, seventy miles east of E] Paso, 
& water-worn mass of syenite, covering nearly a square mile of 
area, rises from the plains to a height of several hundred feet: 
resting against its base is a limestone of Carboniferous age, con- 
taining several species of Productus ; the limestone has Hed 
crevices a foot in width in the syenite, in which several smal 
Se shells, species of Plewrotomaria and Helicotoma were found. 
8 there are no indications of limestone having over seen CO . 
‘posited except near the base of the Cornudos, a portion of this 
tock may have been above water in the Carbon erous sea, — 
