16 
(7) Where not concealed this is a dark grey limestone 
(8) A dark grey limestone, very full of chert concretions; these chert nodules, 
especially in the lower beds, are large, 6 inches to 2 feet in diameter, and very 
irregular. The hardness of these causes the beds to form an outcropping ridge. . . 
These beds might almost be called a fossil coral reef. The rock is espec- 
ially conspicuous for the abundance of Lithostrotion (three species), Aulopora, 
Syringopora, Lophophyllum, and Campophyllum. 
(9) A dark grey, medium-grained limestone, partly concealed, with few 
chert nodules except in the lowermost bed where they are very abundant and are 
often one mass of crinoid joints 
Lithostrotion is conspicuous because of its absence, since in the higher 
beds it is so abundant; its place is taken here by cup corals. 
(10) A dark grey, coarsely to finely grained limestone, friable upon weather- 
ing, partly concealed. Chert nodules apparently absent in the coarse-grained 
beds, a few present in the other beds 
Fossils rare except for some cup corals. 
(11) This locality begins above with a fine-grained, dark grey limestone, 
very full of chert in bands or small but numerous nodules, both developed along 
the bedding plane. This upper bed is full of Spirifer rockymontanus and Pro- 
ductus. Similar limestone is continued downward with an alternation of beds 
rich in chert nodules and beds poor in them; fossils few 
(12) A dark grey, fine-grained limestone, very full of chert in bands and in 
separate nodules 
38 feet 
24 feet 
62 feet 
120 feet 
40 feet 
6 feet 
These chert bands are persistent along the strike and cause this bed to 
outcrop prominently; it is frequently exposed for 15 feet along the dip. 
The upper foot of this chert bed is made up almost entirely of globular 
chert concretions, one-quarter to one-half inch in diameter. These give 
to the weathered surface a peculiar nodose appearance which is quite per- 
sistent along the strike. At the base of this locality is a foot thick, very 
prolific, brachiopod zone. The abundance of shells in this zone, coupled 
with their absence both immediately above and below for a distance of 2 
feet in each direction is very noticeable. The lower part of this shell bed is 
very full of chert nodules enclosing the shells, whereas the upper part with 
just as many shells has no chert. The chert is, as is usual, accumulated at 
the base of this coarse bed. 
The brachiopods are in approximately equal abundance all along the 
strike. The species vary considerably locally, as in modern seas. In one 
place, large adult and old shells of Spirifer rockymontanus occupied the 
sediment almost to the exclusion of young and small mature specimens of 
the same species, whereas 100 feet north these latter are quite abundant, 
with few of the large Spirifers. A fourth of a mile south along the strike 
specimens of ScheUwienella lata strongly predominate. A quarter of a 
mile still farther south, the large examples of Spirifer rockymontanus are 
again prominent. The sediment is apparently similar in all places. 
Throughout this distance the shell bed remains a foot thick with the chert 
confined to its lower half. 
(13) A dark grey limestone, alternately chert-bearing and chert-free 25 feet 
The lowest bed is full of chert nodules and is locally very prolific in 
brachiopod shells. These fossils, as in the shell bed above, vary much 
locally. Where the section was made Producti predominate, whereas a 
quarter of a mile along the strike to the south these had entirely given place 
to Athyroids; a quarter of a mile still farther south Producti again became 
dominant. 
