Geology of Castle Rock.—Lee. 97 
ler, of Chicago University, who determined some of the best 
preserved specimens to be Dalmanella testudinaria and the age 
of the series Ordovician. Other forms are present, but the 
specimens were too poorly preserved for specific identification. 
A second exposure of limestone similar to the first and simi- 
larly placed occurs within the region shown in the accompany- 
ing map, but no fossils were found in it. Its character and 
position, however, are such as to make it probably of the same 
age as the Ordovician of Deadman creek. 
3.—Carboniferous.—It has been known since the time of 
Hayden's survey that Carboniferous strata occur in Perry 
park. Mr. Whitman Cross made a small collection of fossils 
from this formation some years ago. They were identified by 
Mr. George H. Girty, of the United States geological survey. 
My own collection was 7lso examined by Mr. Girty, who has 
kindly furnished me with the following list: 
Orthothetes inaequalis Seminula subquadrata (+) 
Spirifer centronotus Cranaena n. sp. 
Spirifer sp. b. Myalina arkansasan@ 
Spiriferina solidirostris (?) Aviculopecten sp. 
Regarding the age of the formation in which these fossils 
occur, Mr. Girty says in a private letter: “I feel satisfied that 
the horizon is Lower Carboniferous and think it probable that 
it comes in the middle portion, though this is less certain.” 
Fossils occur in a thin seam of cherty limestone, about 
fifty feet from the base of the formation. The fossil-bearing 
seam is exposed in the north bank of the stream flowing 
through the park. At-the-base of the formation occur forty 
feet of coarse-grained, crumbling sandstone, conglomeratic_in 
places, and mottled in varying shades of red and gray. Above 
this sandstone is a series, ten to fifteen _feetthick, of deep red 
to white _cherty limestone in layers, alternating with red 
shale. Near the top of this series is the fossiliferous seam. 
Above is a series of several hundred feet of coarse-grained | 
sandstones and conglomerates which appear to be perfectly | 
conformable with the fossiliferous series. They are colored 
irregularly in various shades of red and gray to an extent 
which gives the series a conspicuous mottled appearance. 
The gray predominates near the base. From thence upward, 
the red becomes prominent and the series passes gradually into 
