SILURIAN SYSTEM : UPPER NAMHSIM STAGE. 



139 



denudation has not proceeded far enough to expose them, or, as 

 in my opinion is the more probable explanation, because this 

 portion of the sea floor was so remote from the coast of that 

 period that the sandy beds were not deposited. I am the more 

 inclined to adopt this view, because the marly, upper Namhsim 

 beds are to be found in most parts of this area, and in places 

 like the Loi-len range, where the covering of limestone has been 

 stripped off over a very large extent of country, there is no sign 

 of any thick bed of sandstone ever having been present beneath it. 



Upper Namhsim Stage (Konghsa Marls). 



In places where the Namhsim Sandstones are well represented, 

 as in the gorge of the Nam-Tu north of 

 Lithological charac- Hsipaw, and in that of the Namhsim above its 



ters and mode of depo- n . . . . . , . . , 



sition. conflux with the former river, they are found to be 



followed conformably by a band of sandy marls with layers or lenticular 

 inclusions of very hard and compact limestone. These beds, though 

 of no great thickness, have been found over a very wide area, extending 

 far beyond the limits of the lower part of the formation. The reason 

 for this comparatively wide extension of the marls appears to 

 be, not that they were deposited in a sea basin gradually increas- 

 ing in area, by subsidence of its shores, but that the sandstones 

 beneath were laid down only in the neighbourhood of the coast. 

 The marly beds, therefore, in localities where the sandstones are 

 not represented, may be partly contemporaneous with the latter, 

 that is to say, that while the sandstones were being laid down 

 along the coast line, the marls were already being accumulated 

 further out to sea, but naturally at a slower rate ; and I think that 

 this hypothesis is borne out by the pala;ontological evidence, 

 which, as we shall see, does not indicate in any way whatever 

 that the two classes of deposits were laid down at distinct periods 

 of time. 



At several localities these beds are found to be richly fossili- 

 _ . ferous, and in spite of their small thickness 



List of fossils. K 



as compared with the sandstones, they have 

 yielded a much larger number of species than the latter. The 

 collections already made, and described by Mr. Cowper Reed in his 

 Memoir on the lower Palaeozoic fossils of the N. Shan States, com- 

 prise the following species : — 



