382 ASSINNIBOINE AND SASKATCHEWAN" EXPEDITION. 



traces of organisation. Below this stratum a layer of sand- 

 stone six feet thick occurs (/), holding spheroidal forms, 

 which vary in size from six inches to two feet in diameter ; 

 they are formed of yellow sand containing a hard central 

 calcareous nucleus often four inches to one foot in thick- 

 ness, and composed almost altogether of an aggregation of 

 Avicula Nebrascana (Evans and Shumard). The stratum 

 in which they are embedded holds Avicula Linguceformis 

 (Evans and Shumard). 



A second layer (g) of large concretions follows, similar 

 in external aspect to those already described. Below them 

 there is a persistent layer of hard calcareous sandstone 

 about four feet thick (A), containing Avicula Linguceformis. 



The lowest stratum exposed is a soft sandstone (i) about 

 six feet above the river, and passing beneath its level. 

 This rock is worn into caves by the action of water. The 

 formation is nearly horizontal, with a slight north-westerly 

 dip. For several miles this upper cretaceous* rock con- 

 tinues to form the river bank. The concretionary masses 

 are persistent, bold, and prominent, and about three miles 

 in a north-westerly direction from the point where they 

 were first observed, those of the lower stratum are nearly 

 on the same level as the water, thus showing a north- 

 westerly dip of about three feet in the mile. 



The banks of the river slope gently from the prairie on 

 the south-west side to an altitude of about 250 feet above 

 it, they then assume the form of steep declivities. On the 

 north-west side the sandstone cliff rises abruptly from the 

 river to a height varying from thirty to sixty feet, when 

 it meets the foot of an undulating slope which extends to 

 the prairie level. Trees, consisting chiefly of aspen and 

 the mesaskatomina, are found in patches on both sides. 

 The river continues for many miles about 700 yards 



* See Chapter on the Cretaceous Series, Vol. II. 



