STRATIGRAPHIC POSITION OF JUDITH RIVER FORMATION 545 
Mactra formosa M.&H. These have been identified by Dr. 
Stanton, who says: ‘‘This lot is apparently made up of collections 
from two distinct horizons. The first five species of the list are 
from the upper half of the Claggett, the other two probably from 
a lower bed which may also be in the Claggett or possibly as low 
as the Eagle.” 
There is no mixing of horizons stratigraphically, as all of these 
specimens collected by the writer came from an area that can be 
included within one’s outstretched arms, in which the exposure is 
perfectly shown; therefore they are all from the Claggett of Dr. 
Stanton, or, according to the writer, from the Fox Hills formation, 
as the species are found in the Fox Hills of Colorado and other por- 
tions of the Rocky Mountains. The fact that two of the species 
are mentioned as “‘possibly”’ of Eagle age and these two rather 
widely distributed in the Fox Hills raises the question as to whether 
the sandstones occurring so frequently along the Missouri River 
and supposed to be brought to the surface by faulting may not be of 
Fox Hills age rather than of Eagle age, especially as lithologically 
they are almost indistinguishable. It was impossible, as already 
intimated, to unravel the structure here in the few hours we spent 
at this locality. 
Returning to Fullerton we crossed the county to the eastward, 
the surface formation until we reached Dog Creek being the beds 
of the Judith River formation. East of Dog Creek the faulting 
was again in evidence, beds of Pierre and Judith River age mainly 
being involved, although it may be found later that the Eagle 
sandstones and Belly River formation are present in some of the 
ridges. So much of the surface of this area is covered and the lines 
of the faulting so numerous (there being at least six of them sepa- 
rated by areas of Pierre shales) that no attempt was made to 
unravel the complicated structure. Until a complete areal survey 
is made, the structure here must remain obscure. At Mauland 
(now known as Boe’s ranch), which is about ro miles south of the 
Missouri and about 20 miles east of Dog Creek, well-marked expo- 
sures of Judith River, as determined by fragments of vertebrate 
remains, were seen at the ranch dipping steeply (20° to 25°) against 
a fault-line, separating them from the Pierre shales, which are 
