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interesting association of Cretaceous forms, consisting of numerous 

 Inocerami and Ostrecv, besides Ammonites, Scaphites, BacuUtes, and the 

 fragmentary remains of fishes, representing at least two Teliostean gen- 

 era and a Squaloid Oaleocerdo. In the plains east of the Canadian, simi- 

 lar and more extensive limestone deposits are known to occur, which 

 are reported as containing the same faunal assemblage. 



Post- Tertiary. — From the base of the abrupt western boundary of the 

 basin, the Cretaceous shales descend in gentle interrupted slopes far out 

 into the valley, and which at one time must have formed a continuous 

 shelving beach-like declivity along the flanking hills. But in the pro- 

 cess of the drainage of the basin and the consequent deepening of the 

 channels of the numerous streams which come down from the mountains 

 and neighboring table-lands, this sloping terrace was subjected to exten- 

 sive erosion, uutil it now presents the condition of so many terrace- 

 benches descending into the plain between the embouchures of the little 

 valleys. They present all the phenomena of the Terrace epoch, not- 

 withstanding they are wrought out of the Mesozoic deposits, and the 

 mouths of the larger valleys are occupied by series of terraces in all 

 respects resembling in form and position those which, in other parts of 

 the country, are entirely made up of re-arranged drift materials. 



The terrace-benches which fill the mouth of the Cimarron Valley may 

 be regarded as typical examples of these formations, in the molding of 

 which the waters of the Cimarron have played an important part. Here 

 there are at least four or five well-defined benches, ranging in height 

 above the present level of the stream from a few feet to 300 feet. The 

 two highest of these benches, which now occupy the divide between the 

 Cimarron and Cimarroncito, are, however, themselves probably but 

 remnants of the old lacustral beach which once extended continuously 

 along the foot of the Tertiary plateau. The lower and by far the most 

 extensive of these old benches attains an elevation of about 200 feet, 

 forming a low mesa extending along the south side of the stream a dis- 

 tance of three miles. Its summit gradually slopes toward the plains, 

 and, like the preceding, is clothed with a thin layer of coarse drift, the 

 degradation of which has thickly strewn the declivities with small bowl- 

 ders and pebbles, effectually concealing from view the Cretaceous shales 

 upon which it rests. This mesa has been pierced by two or three lateral 

 arroyas, besides the little valley which intervenes between its western 

 extremity and the foot of the Tertiary-capped hills, in the sides of which 

 natural sections of the fossiliferous Cretaceous shales are exposed at 

 various points. The next distiiict bench is that which occupies so con- 

 siderable an area along the south side of the stream, and which drops 

 to the level upon which the town is principally built, though it continues 

 to follow the stream lower down, but much diminished iu width. Above 

 the town, this beneh reaches the height of 50 to GO feet, and at a point 

 where its base is washed by the stream an interesting section is exposed, 

 showing the character of the superficial deposits which here deeply cover 

 the terrace. The lower 30 feet or more of the exposure is made up of 

 dark-blue shales of the Cretaceous period. Kesting upon these occurs 

 a heavy deposit of modified drift, the lower portion of which is appar- 

 ently largely composed of sand with streaks of gravel ; the upper six 

 or seven feet exhibit a distinct deposit, made up of water-worn bowlders, 

 pebbles, and gravel, which seems to immediately underlie the fine soil 

 with which the terrace is mantled. 



Similar exhibitions of terrace-formations, as before stated, are met 

 with in the mouths of all the valleys penetrating the great Tertiary pla- 

 teau, and perhaps nowhere are they more conspicuous and symmetrical 



