Pembina Region of North Dakota — Berkey. 147 
weathered bluffs where B is exposed, a few good fossils 
typical of the Niobrara have been found by the writer. 
Ostrea coiv^esta Conrad, is the most common. Fragments 
of a large shell of fibrous structure and prominent parallel 
ridging are also common ; they probably belong to Ino- 
<:eramus platinus Logan. In one case a fragment of this 
form was found replaced by iron pyrite perfectly preserving 
the structure. 
The mosasaurs are also represented. One fragment 
of a lower jaw carrying four teeth and a couple of verte- 
bra were found at the Mayo location. A large fish verte- 
bra and the fore part of the upper jaw carrying stubs of 
teeth were found at the same place. They belong to the 
Portheus of Cope. Together the few forms found serve 
to determine the age of these marl beds as Niobrara. At 
Tongue river both fish and mososaur remains fairly com- 
plete have been reported from the cement bed. 
No fossils have been observed in the shale beds of 
division A, here credited to the Benton formation. 
The eastern edges of these formations are exposed in 
the stream gorges of the "second Pembina mountain." 
Rarely can all be seen at any one point, but this portion 
of the Cretaceus series is readily made out and followed. 
What there is below .\ or above E does not appear in this 
area. 
Local and Econoviic Drscripiions . — The Tongue River 
Section Tongue river cuts deeply enough into the second 
mountain to expose all the beds down to and including the 
cement beds. A short distance above the entrance to this 
gorge where the marl zone is particularly prominent the 
Tongue river cement plant is situated. At this point it is 
about 70 feet from the bed of the creek to the base of the 
black and white bands of bed D above. Both D and C are 
in typical development, but only about 50 feet of the brittle 
shales of bed E are exposed because of drift and slide from 
the bluff. 
Cement manufacture has been the chief attraction here. 
The plant is making a natural cement that is claimed to 
have unusual quality. It is certainly giving good satis- 
faction to local patrons. An extensive plant was installed. 
