Art. IX.] Herrick-Johnson, Geology of the Albuquc^'que Sheet 189 
the same peculiar concretions and identical fauna. From this 
bed we have recognized a considerable series of fossils men- 
tioned in the list given beyond. Above the cephalopod zone 
and the sandy shales overlying it is another large band of dark 
and yellow earthy shales at least 100 feet thick capped by mas- 
sive sandstone perhaps 50 or 75 feet thick. This we have called 
the Punta de la Mesa sandstone because of its prominence at 
the place so called north of San Ignacio in the Rio Puerco 
valley. 
The upper part of this series which is separated from the 
lower by a shaley portion has a varied fauna though the state 
of preservation is not all that could be desired in most cases. 
The Punta de la Mesa sandstone is undoubtedly of Fox Hills 
age though it has been very incompletely studied. Above it is 
an extensive series of mostly loose yellow sandstone with shaly 
phases which is not easily estimated. The section given on 
Plate XLVIII, No. i is from the east side of Prieta mesa north of 
our sheet but does not reach the top of the series. The fossils 
so far as preserved seem to be identical with those of the Punta 
de la Mesa, with others so far only found in the lignitic division 
above. We may estimate this series of Prieta sandstones at 
1000 feet thick. It is well exposed in the low hills east of 
Punta de la Mesa on the east side of the Rio Puerco and here 
is followed by the upper or 
The Ltgnitic Division. 
This group is best seen east of the locality last named north- 
east of San Ignatio some three miles. The strike is south-west 
and the same series is thus exposed west of San Ignatio, the con- 
tinuity of this area with the previously mentioned being broken 
by the intervening Puerco valley and flood plain. The series 
as exposed at the northern part of this area is as follows: The 
Prieta series occupying low hills east of the river for perhaps 
one quarter of a mile. These yellow sands and flags are greatly 
weathered and do not enable us to give an accurate section. 
They are followed by fifty feet or so of white sandstone with 
ferrugineous layers, 35 to 40 feet of lignite, 5 feet of white 
