22 FAIRBANKS AND RAMPART QUADRANGLES. 
The minute characters used for specific limitation in corals are not well 
enough preserved to justify any attempt at the specific determination of the 
corals. Since the genera noted above are all common to both Devonian and 
Silurian horizons, they afford no definite evidence as to which of the two 
the corals represent. The chief interest of the collection lies in the lamelli- 
branch fragments, which represent a very large, thick-shelled form that ap- 
pears almost certainly to be specifically identical with a shell occurring in the 
limestones of Glacier Bay and similar beds at Freshwater Bay in southeastern 
Alaska. This southeastern Alaska shell has been referred to the genus Mc</<t- 
lomus and considered to belong to a late Silurian fauna. 
7 AF 318 and 7 AF 320 (Head of Little Minook Creek). This material 
has yielded four or five species of brachiopods, represented by very poor frag 
ments, so thai even approximate determination is difficult. They may be ten- 
tatively referred to the following genera : 
( 'honetes? Amphigenia ? 
Stropheodonta. Rhipidomella V 
Delthyris? 
The determination of Stropheodonta is based on a fragment of a single 
valve, but the distinctly denticulated hinge line leaves but little doubt of the 
correctness of this generic determination. This genus is unknown in the 
Carboniferous "and is emphatically characteristic of the Devonian." Amphi- 
genia, which is believed to be represented by a fragmentary mold of a pedicle 
valve, is also limited to the Devonian. The specimen referred to Delthyris? 
is unique in its ornamentation and may possibly belong to another genus. 
There are also two other doubtfully determined genera of brachiopods, repre- 
sented by fragments. The small gasteropods, which are represented by molds 
belonging to two or three species, contribute no evidence as to the age of the 
fauna. Although more and better material is needed to determine the horizon 
with certainty, it is believed that the forms determined as Stropheodonta and 
Amphigenia? necessitate placing the fauna in the Devonian, at least provi- 
sionally. 
The occurrence of this fauna in conglomerates interbedded with black shales 
leads me to believe that it belongs near the top of the Devonian of the Yukon 
section, in beds corresponding to the black shales of the Calico Bluff section. 
The fauna is quite unlike any other Alaskan fauna which has come under 
my observation, but for the reasons already stated it should, in my judgment, 
be placed provisionally in the Devonian. 
CARBONIFEROUS. 
At the extreme northern limit of the hill country, in a minor ridge 
bordering Yukon Flats; there are greenish, grayish, and black slates, 
with siliceous material, scattered fragments of which were found to 
contain fossils indicating a Pennsylvania!! or Permian age. At an- 
other locality, about 15 miles farther southwest, just south of Hess 
Creek, fossils also regarded as Carboniferous were found in soft, 
black carbonaceous shales. At both localities the rocks are in close 
association on the south with cherts and slates. It is possible that 
there is a fault between the two formations, and the relation is so 
represented in the section. All that can be affirmed at present is that 
in the northern part of the area there occur Carboniferous rocks, 
