160 
STRATIGRAPHICAL GEOLOGY 
As first distinctly defined by Herrick the Sandia formation 
referred only to about 100 feet of shales and thinly bedded lime¬ 
stones, and this terrane is sharply separated from the superincum- 
bant 600 to 800 feet of dark limestones, which in turn are again 
followed by gray limestones. It is extremely doubtful whether 
the basal Sandia shales are represented at all in the Magdalena 
and Socorro mountains 100 miles to the south. It is certainly 
quite inadvisable to try to expand the term Sandia formation be¬ 
yond its original limits. 
If the blue and grey limestones below the reddish shales of the 
Sandia and Manzano ranges are to be thrown together, which 
seems very unwise, the term Magdalena group recently proposed 
is clearly synonymic. Richardson’s title of Hueco Group seems 
to cover the section exactly, and has the great advantage of being 
at least recognizably defined. 
The Maderan series appears separable from the Manzanan 
series upon the same faunal, as well as other grounds, as the Mis¬ 
sourian and Oklahoman series in Kansas. It appears as a three¬ 
fold series, as exposed in the north in the Sandia mountains, the 
main limestone member being only about 400 feet in thickness. 
This member becomes rapidly thicker to the southward, possibly 
reaching a total thickness of over 3,000 feet. This superior lime¬ 
stone part, or Maderan member, is included in the Hueco forma¬ 
tion of the Trans-Pecos Texan region. If the name Hueco is to be 
retained it could be probably made to fit the median member. To 
the third and uppermost member, composed of shales and sand¬ 
stone having a pinkish or reddish coloration, the title Bernalillo 
shales cannot be very well set aside. 
There is surely some grave misconception in regard to the 
usage by Mr. Lee of the term Maderan formation. As a geologic 
title the name was never used in print by Professor Herrick, as 
is stated. By me the term was distinctly applied to the Carbonic 
limestone section in the Sandias, above the dark limestone to 
which was given the name of Manzanan series. In the Magdalena 
mountains I do not think that this formation is at all represented. 
Of exceptional value are Dr. Girty’s tabulated paleontologic 
data. As in the case of his similar records of the Carbonic faunas 
of Kansas, the facts displayed furnish some of the best possible 
proofs that we have of the invalidity of many of the more purely 
stratigraphic contentions. 
