E. Bose — Permian of Coahuila, N. Mex, 191 



probably can be determined specifically. The Staclie- 

 oceras belongs to the group with numerous saddles, 

 and resembles forms from the Sosio beds of Sicily. Of 

 Richthofenia I found only one specimen, but the other 

 brachiopods are numerous. The small Myalina is very 

 common. 



From this level upward in the series clays and sand- 

 stones predominate ; but about 50 meters higher we find 

 a zone of imperfectly bedded dark gray limestone con- 

 taining silicified fossils, mainly those described by Haack 

 from the Pichagua cliff. Then follows more dark clay 

 and sandstone, and finally a bed of dark limestone with 

 fossils, only about half a meter thick. Above comes more 

 dark clay and some sandstone and then a mass of partly 

 well bedded dark gray siliceous limestone at least 20 

 meters thick. I call this locality Malascachas No. 4. The 

 limestone here contains a great number of silicified 

 fossils, most of which belong to Richthofenia cf. 

 permiana, and can be collected by the hundreds. There 

 are also corals, and Composita afe suhpolita, TJncinulus, 

 and other brachiopods, as well as Bryozoa. As in all the 

 lower beds, w^e likewise frequently find here crinoid 

 stems, some of rather large diameter. 



In its upper portion the limestone dissolves into 

 blocks and concretions imbedded in dark clay, then fol- 

 lows more dark clay for about 20 meters, and this in turn 

 is covered by a green sandstone of igneous detritals. 



This sandstone is unconformably overlain by light 

 colored hard limestone containing oysters and, a little 

 higher up, Orhitolina texana. The limestone is medium 

 bedded and has a thickness of about 50 meters; in its 

 upper portion it passes into dark dolomites and light 

 colored thick bedded limestones alternating with beds of 

 white gypsum. The dolomite frequently contains in the 

 lower portion beds composed of Monopleura and higher 

 occur thick beds of light colored or reddish limestone 

 almost entirely composed of medium-sized Caprina or 

 related genera. Then follows the main mass of the 

 middle Cretaceous limestone composing the upper portion 

 of the Sierra del Sobaco. 



The gypsum band of the Cretaceous is extremely char- 

 acteristic and can be distinguished from afar. It forms 

 a light-colored band along the whole Sierra del Sobaco, 

 and where the large north and south fault cuts the beds, 

 we see one whitish zone of gypsum high in the mountains 



