28 The American Geologist. Jan. 1891 
a small gryphaean, the American analogue of the former. An- 
other prominent variety has the beak much less produced and the 
umbonal slope radiately grooved or striated. 
No. ."> yields also a species of Polyzoan and vertebras <>f a 
plesiosaurid. 
The Gryphcea of the lower part of No. 2 of this section are of 
remarkable size, ranging from three to four inches in hight, and. 
at a locality nearly a mile east of the Blue Cut, equally large ones 
occur at the same horizon. One of the latter reaches a hight of 
four and three-eighths inches ; it is of the typical triangular form. 
Nos. 4 and of the Belvidere section, followed "up the .Medi- 
cine Lodge river and Otter creek, can be traced to within about a 
furlong of the Blue Cut,* where they pass beneath the Level of 
the Otter creek valley, the horizon of the sandstone probably pass- 
ing under the Blue Cut at a depth of between thirty and forty 
feet below the floor of the cut. 
On the north slope of a ravine which skirts the Blue Cut mound, 
and but a few rods distant from the latter, occur, in yellow shales. 
lamina? of yellowish gre}' sandstone, or arenaceous limestone, con- 
taining numerous small, rostrate, entire-margined bivalves of un- 
determined genus, with occasional specimens of Cardium kan- 
8asense, Cyprimeria crassa, and a rather large species of Tnocera- 
Ni us. Of these forms, the first characterizes No. 2: the three 
latter, No. 3 of the Belvidere Section. In its lithology and in the 
state o/ preservation of its fossils, this horizon resembles No. 2 
of the Belvidere Section. It probably represents a passage-hori- 
zon between Nos. 3 and 2 of the Belvidere Section. It has not 
been detected in the Blue Cut Mound section proper, where, if 
present, it is probably to be found in No. 4, the fossils of which 
are still unexamined. 
The above-mentioned contact of the Dakota upon the Neocom- 
ian is shown in the following section of the bluffs near the head 
of West Bear creek in Clark county : 
*The " Blue Cut" is on the line of the C. K. & ^V. Railway, a few 
miles S. S. \Y. of Belvidere. The Belvidere Section includes a ravine 
and a hill at the top of the same, half a mile to a mile nearly due south 
of Belvidere. 
