E. Bose — Permian of Coahuila, N. Mex. 189 



toward a small creek, where it could be easily observed 

 that it was normally lying between the sandy and shaly 

 beds of the Delicias formation. I then resolved to study 

 the relation between the cliffs and the Delicias beds in 

 another portion of the valley where I could also find 

 sufficient drinking water, and where the Delicias beds are 

 much better exposed than in the Arroyo de Wenceslao. 

 This place is a few kilometers farther south, near the 

 Noria de Malascachas, where a well dug in the Delicias 

 beds contains plenty of good water, a rather scarce 

 commodity in this region. 



Here the Delicias beds compose the lower half of the 

 Sierra del Sobaco and show in several places cliffs of dark 

 limestone. I tried to make a cross-section and to collect 

 as many fossils as possible. 



A little east of Noria de Malascachas the Delicias beds 

 are cut off by a north-south fault which toward the east 

 brings the series into contact with a block of Cretaceous 

 limestone. The lowest portion of the Delicias exposed 

 here consists mainly of dark, thin-bedded or laminated 

 clays, alternating with thin to thick beds of greenish to 

 yellomsh sandstone, mostly of igneous detritals. Some- 

 times the clays contain concretions of dark limestone with 

 scattering remains of undeterminable brachiopods, and 

 often Fiisulina. The beds show a strong dip (45" and 

 more) toward the west. These rocks continue for about 

 150 to 200 meters higher stratigraphically ; then the sand- 

 stone becomes coarser and passes into a conglomerate, 

 mainly of igneous material, the pebbles being large and 

 well rounded. Upward in the conglomerate occur cal- 

 careous concretions which also pass into the dark clay 

 and a few meters higher consolidate into a bed of lime- 

 stone. This forms -a small cliff on the crest of a spur of 

 the mountain but continues in the creeks on both sides 

 of the spur, without any interruption, as a solid bed of 

 dark limestone, becoming somewhat thinner with distance 

 from the lenticular swelling of the cliff. Higher strati- 

 graphically the bed of limestone dissolves into a great 

 number of rounded blocks. These apparently are only 

 concretions imbedded in dark clay, and about half a meter 

 above the solid bed of limestone the dark clay predomi- 

 nates, reproducing here, as elsewhere, intercalated beds 

 of greenish sandstone. There can be no doubt that the 

 limestone is interbedded in the clay, sandstones, and 

 conglomerates of the Delicias beds, and that the little cliff 



