
| 
CRETACEOUS AND TERTIARY—SOURIS RIVER. 91 
very full of shells, which are also less crushed and in a better state of 
preservation than is usual in this formation. The most common 
Molluse is Melaniu Nebrascensis M. & H., which occurs in all stages 
of growth, and several varietal forms. There is also a second species of 
this genus, or of Goniobasis ; fragments of Unio and Paludina; and a few 
examples of Corbula (Potamomya) mactriformis M. & H. The latter 
must be considered a brackish-water type, but with this exception, no 
brackish or salt water forms are found in these sections of the Souris 
Valley. The Mollusca exactly resemble those of the Fort Union or Great 
Lignite Group of the Missouri, and fix with certainty the stratigraphical 
position of the beds here represented. 
214. In the water of the stream, at this place, are several large 
spheroidal sandstone concretions which have a tendency to split into 
layers parallel to their flattened surfaces—one of them measuring four or 
five feet in diameter. These do not appear in the bank, but possibly may 
have been washed out of the lower part of the section, which was not so 
clearly shown. 
215. South of the last section, and about one mile nearly due north 
of the position occupied by Wood End Depot, an exposure, showing the 
most valuable dignite bed I have seer in the Souris Valley, is situated. 
The beds are arranged thus :—(Plate 3, Fig. 1.) 
FEET. IN 
1 Dre manorial Mabon) is}. b 3. hoor bs org oh hands Hose Sak ds 8 0 
2. Yellowish and grey stratified sandy glays, obscured in most 
places by ne Ge ee as ied he eA eset 52 0 
SE aE Se Ee ae oe ae ney Ree 7 3 
ig Rete MOIR REE = a8. 'da'aias nin wae ow aware a niase 1 or more. 
216. The bottom of the lignite is about twenty-five feet above the 
level of the river below, and this part of the section, though apparently 
consisting of yellowish sandy clays like those overlying it, is obscure. 
The lignite is continuously visible for at least two hundred feet along the 
face of the bank, and seems to preserve uniformity of character and thick- 
ness. Externally it is often crumbling, and mixed with clay which has 
penetrated its joints from above; but where freshly exposed, it is hard 
and compact. It is quite black on freshly fractured surfaces, but has a 
brown streak, and in many places the structure of the original wood 
is still quite discernible. Some surfaces are strewn with fragments of 
mineral charcoal like that found in many true coals. Other specimens 
are apparently structureless, and resemble cannel coal in appearance, 
though notin composition. The upper beds of arenaceous clay yield a few 
poorly preserved shells (Paludina, &c.) 

