248 



THE CANADIAN NATURALIST. [YoL A'H. 



^eat thickness are excellent in quality. Bed No. 18 is one of 

 the very few instances where a well characterized underclay was^ 

 found to lie below a bad of lio-nite. 



Few recognizable remains of plants are found in this part of 

 the region in conuection with the lignites. Some beds, however, 

 and often those in close association with the lignites, yield mol- 

 luscan remains, representing two species of Pahtdina or Vivipara 

 at least two oi' MeUmia, one Corhnla and several Unio-Xxko, bival- 

 ves. All these resemble those described by Meek and Hayden, 

 ftom the Lignite Tertiary further South, and the Corhula is 

 probably identical with their C. mactrlformis, and indicates that 

 brackish as well as fresh waters took part in the deposition of" 

 the lower beds of this formation. 



Another peculiar feature in connection with the lignite deposits 

 is their tendency to burn away in situ, and below the surface of 

 the ground. The beds become ignited by some prairie fire, or 

 the camp-fire of some Indian or trader, or it may be spontane- 

 ously (though this seems improbnble, as iron pyrites, the general 

 agent of spontaneous combustion in coals, is absent in these lig- 

 nites) ; and smoulder away for years, producing breaks in the 

 edges of the bank by the caving in of su}>erior beds-, and giving 

 rise to a material which is plentiful in many plaees, and resembles 

 a scoriaceous lava, but is really a species of elinker produced bjr 

 the fusion of the ashes of the lignite. 



In continuing westward, and after h ivin'ji; crossed the regrioQ 

 of drift hills already mentioned as the Coteau de Missouri, the 

 Lignite formation is again represented in all the valleys and gullies 

 of the streams which now run southward, and form the upper parts 

 of the North Western tributaries of the Missouri. Specially 

 good exhibitions of the rocks are to be seon in the first of these 

 large valleys, at a distance of 345 miles west of R.'d Riv^er, and 

 also in another a few miles further west, which has been called 

 Pyramid Creek, from a remarkable pyramidal hill formed by 

 the wearing away of the softer beds of the forn> ition from below 

 a layer of harder sandstone, a block of which has formed the 

 capping of the hill. The beds are everywhere nearly horizontal,. 

 .showing merely local dips, and it does not appear that a great 

 thickness is represented by the whole of the sections examined^ 

 One locality is remarkable as showing the greatest development 

 of the lignite beds, and also for the abund mce of remains of 

 plants in moderately good preservation. This is ncarij 40^ 



