40 DESCRIPTION OF THE FOSSILS. 
In the letter of Charles L. Taplin, addressed to Captain Pope, mention is made of: ledges of 
petrified oyster-shells from this locality.! 
No. 82. A specimen labelled ** Neocomian limestone from the Elm fork of the Trinity river. —It 
consists of fragments of Gryphcea, firmly impacted together, and so obscure that the species 
cannot be determined. It resembles G. Pitcheri, and in the mineral characters so closely simu- 
lates specimens obtained by Major Emory, and containing Cretaceous fossils, that it must be 
regarded as coming from the same formation. There is certainly no evidence of its being of 
the age of the Neocomian division. | 
PRODUCTUS. 
No. 91. From the bed of an affluent of the Elm fork of the Trinity river.—These two speci- 
mens are compact limestone, of a dark color, and much stained with oxide of iron. They are 
marked by casts of fossils, which, though Shere: are of Producti, and indicate, for the speci- 
mens, the age of the Carboniferous. They are, undoubtedly, transported fragments from out- 
crops of the Carboniferous limestone. 
REMARKS. 
The fossils which Captain Pope has collected, with the exception of No. 91, are all such as 
characterize the Cretaceous formation. This formation is well represented by Gryphcea Pitcheri 
and Exogyra Texana from the Big springs of the Colorado. These fossils are well known in 
the 
as formation of Texas. The former was first described by Dr. Morton, of Phila- _ 
delphia,? “who received his specimens from the plains of Kiamesha, Arkansas. He ele states 
that he has seen other specimens from the falls of Verdigris river, in the same territory. 
These fossils serve to indicate the development of the Cretaceous formation at the following 
points: Banks of the Red river, near Preston; Big springs of the Colorado; Elm fork of the 
Trinity river; and a point twenty miles east of the Sand hills, on the Llano Estacado. I have 
therefore colored these places as Cretaceous upon the map. 
H 
! Report of Captain Pope, p. 77. * Morton's Syn. Org. Rem. Cret. Groups U. S., p. 55. 
Or e ERR 
