462 PROCEEDINGS OF THE ACADEMY OF [1890. 



ant, and they can be readily identified on the polished surfaces of 

 the marbles which are worked in the village of Nogales. I deter- 

 mined here various forms of Hippuritidte — Hlppuriies, Radiolites, 

 Ichthyosarcolithes — Nerincea Castilli, the species of Nerincea referred 

 to by Barcena as N. Meroglyphica and N. Goodhalli, a species of 

 Murex, a large Actceonella (?) or possibly Tylostoma, and the oyster 

 which Barcena has identified with Ostrea virgula. The Escamela 

 Mountain, as determined by Guillermo G. y Puga, rises 1417 feet 

 above the valley, or to absolute height of some 5800 feet. To the 

 opposite side of the town of Orizaba the Borrego presents a steep 

 face, some 800 feet in height, of heavily bedded blue limestones 

 whose general dip is to the south w'est. I found no fossils in this rock, 

 and I suspect that it belongs to a somewhat different horizon from 

 that of the gray marbles of the Cerro de Escamela, but I could not 

 absolutely satisfy myself as to its true relations. 



In the valleys leading out from Orizaba there are a vast series of 

 river deposits, which appear here and there exposed in massive 

 stratified beds of shingle, sand, and trap boulders. The section along 

 the Metlac, whose one face is bounded by limestone, well exhibits 

 this feature. But I could nowhere find any evidence of interbedding 

 with the limestone such as Guillermo G. y Puga represents in his 

 geological section along the line of the Mexican Railway from 

 Orizaba to Vera Cruz.^ These river deposits are all comparatively 

 recent, and can be traced almost completely across the coast-land to 

 the sea. 



Between Orizaba and the eastern crest of the plateau the lime- 

 stones, rising higher and higher, are exposed in almost continuous 

 section. In the deep gorge of the Infierno, below Maltrata, the 

 shattered and contorted beds form a wonderful exhibit, and bear 

 witness to the trenipndous strains that were impressed upon the 

 rock-masses at the time of their uplifting. It seems to me probable 

 that the mountains about here have sutiered secondary dislocation, 

 having been warped and twisted from a primal position through 

 successive volcanic squeezes and discharges. Along the northern 

 face of the gorge heavy beds of lava, representing probably an 

 early discharge from the Sierra Negra, rest directly upon the lime- 

 stone, which appears, however, to have suffered but little alteration 

 through contact with the igneous mass. Above Maltrata the rock- 



1 La Naturaleza, 1888, pp. 49-53. With little doubt the section was in- 

 advertently drawn in its present form to represent interbedding. 



