LARAMIE PLAINS. " 89 



strikes and northerly dips. Six miles east of Como Station, the country 

 presents a somewhat strange appearance ; the arenaceous clays on the 

 south side of the railroad being traversed by numerous cracks or fissures, 

 which suggest earthquake-openings or crevasses in glaciers. They are, 

 however, the courses of old stream-beds, now dry, except in seasons of 

 unusual flood and freshet : some of them are but two or three feet wide, 

 and at least 200 feet deep, with nearly precipitous walls of clay. On the 

 north side of the railroad, a broader drainage-channel affords a good 

 exposure of these beds, which, without doubt, belong to the Fort Benton 

 division of dark blue 'days, with layers of fine-grained, hard ferruginous 

 clays and marls, carrying large numbers of fossils of the genera Inoceramus 

 and Ostrea ; while in the more fissile slaty beds imperfect remains of fish 

 appear abundant at certain horizons. 



On the top of the clay wall, close by the railroad, occurs a layer of 

 brown medium-grained sandstone, which derives some interest from its 

 having been quarried at one time quite extensively by the railroad company 

 for building as well as for construction purposes, and transported for long 

 distances. The formation belongs to the sandstone strata, which characterize 

 the Fort Benton division, and, although it in no wise appears superior as a 

 building stone to other similar beds, it may, from its position and occurrence, 

 be worked to great advantage. The lines of bedding are distinctly marked, 

 the blocks quarrying from one to two feet in thickness, with the formation 

 lying inclined at an angle of from 2^° to 3^°. 



Embedded in the sandstone are found numerous fragments of stems 

 and deciduous leaves, most of them in a very imperfect state of preservation. 

 It is possible, however, that a collection might be made sufficiently well 

 preserved to allow of specific determination, which would be of considera- 

 ble importance, as the sandstone, which is about 60 feet in thickness, lies 

 between well-defined beds of the Colorado group. 



The sandstones are overlaid by bluish- gray marls and clays, which 

 probably belong to the Niobrara division ; at least, the latter formation 

 occurs not far distant, with the well-characterized yellowish- white chalky 

 beds, and the sandstones cannotbefar below the junction of the two groups. 



