350 The American Geologist. Tune, 1892 
Trinity sands. It differed, however, from the beds previously 
referred to this horizon in Texas, in the fossils which were found 
in it. These consisted of anoyster which differed from O. frank- 
Jini Coquand, and is now recognized as a new species, Pleurocera 
strombiformis Schloth, Exogyra texana Roemer, Gryphwa pitch- 
eri Mort. The association of these fossils in this way had not 
been reported previously, and in order to be certain of their ex- 
istence together in the same stratum we dug into the bed far 
enough to prove it absolutely. Since later investigations have 
shown the ‘‘Alternating Beds” to be a part of the Trinity sands, 
and the fussiliferous part, and that at their thinning out on the 
northern border the fossils still continue for a limited distance in 
a caleareous sand, this bed would seem to indicate a similar con- 
dition at this locality, and that it should be referred to the ‘‘Al- 
ternating Beds” of the Trinity division: Otherwise it would ap- 
pear to be a transition bed between the Trinity sands and the 
Comanche group. 
Underlying the yellow sand are twelve feet of purple and mot- 
tled sand which are very gypsiferous, and below them we find a 
bed of cross bedded indurated sands. <A few bright colored peb- 
bles are scattered through this bed and seem to be of somewhat 
larger quantity toward the base, In this bed are also found the 
botryoidal layers of sandstone so often observed in the same beds 
to the east. 
3a. Triassic. 
The basal crossbedded sands of ine Trinity rest with slight un- 
coaformity upon a series of purple, red and mottled sands which 
pass at the bottom into a conglomerate of bright colored pebbles. 
The same bright colored pebbles are found scattered through the 
bed from bottom to top singly and in nests or even forming thin 
strata in places. Although in the original section it was referred 
to the Trinity, the character of the material is now known to be 
identical with that described under the name of Dockum beds 
in the first annual report of this survey, and it is, therefore, 
referred to the Triassic, although we were unable to find fossils 
at the Double mountain locality such as occur in the beds near 
Dockum. 
These beds have a total thickness of thirty-five feet. 
All of the deposits included in the Triassic and Cretuceous have 
a slight dip iowurds the southeast. 
