336 TJic American Geologist. June, i90(> 
ilie "'red series," called for convenience tlie "red beds," with 
a very complete Permian fauna, including such species as 
Pseudomonotis havvni, Pseudomonotis strialus, Bakevellia 
parva, Pleurophorus subcuneatus, Aviculopecten occidentalis, 
etc. The upper part of the red beds is not fossiliferous and in- 
dicates a transition to shallow-water conditions, introducing 
the age of salt and copper as well as of gypsum. At the 
southern extremity of this mesa is a group of salt springs evi- 
dently-derived from these beds. In fact, everywhere through- 
out the territory as well as in Texas and Kansas the red beds 
are highly charged with salt and gypsum. These springs are 
also carbonated and form raised mounds about their openings. 
South of the Rio Salado, which forms the southern bound- 
ary of this mesa, is a fine exposure of the next member of the 
series, namely, the gypsum. The gypsum extends in beds 
often over fifty feet thick along the western base of the mesa 
and northward to skirt the Jemez mountains on the west for 
many miles. A curiovis instance of a focus of depression is 
afforded by the Serrita mesa, as the plain at the south end 
of the Jemez range is called. On the eastern and western 
sides the margin is uplifted and lilted toward the axis of the 
range. The gypsum beds appear near tlie base on the west 
side, while on the opposite side of the narrow valley the gyp- 
sum is at the top of the exposure. An amphitheatre is thus 
formed, the Necimiento amphitheatre, with a wall of red beds 
capped with gy-psum extending from the south end of the 
[emez mountains proper west for a short distance, then sweep- 
ing south, tlience turning cast to arch about the south end 
of Serrita mesa. A section of the wall is as follows: 
Feet. 
Gypsum and calcium anhydride 5° 
Vermicular gypsiferous shales lo 
White sand 15-20 
Pink sandy shales 62 
Red sandy shales 5^ 
Massive shales and sandstone 10 
Maroon shales 77 
Unexposed 44 
Continuing downward, after a hiatus of no great dimen- 
sions, we should find the limv lavers at the base of the Per- 
