254 LA TOUCHE : GEOLOGY OF NORTHERN SHAN STATES. 



A glance at this table will show the complete dissimilarity that 

 exists between the fauna of the Wetwin Shales 

 ^Conditions of deposi- and that of the p a d au kpin coral-reef, not only 



in its composition but in its affinities. As 

 Mr. Cowper Reed suggests {Op. cit., p. 183) this difference may be due 

 as much to bionomical surroundings as to a difference in age, and indeed 

 it is evident that the two sets of beds must have been deposited under 

 very different conditions. It seems probable that the shales were 

 accumulated in a lagoon which may have had only a slight connection 

 with the open sea, and in respect to this supposition it is interest- 

 ing to note that a portion of the shales is highly impregnated 

 with iron ore, which may have originated, as so often happens, 

 in a shallow swamp or lagoon. The deposition of the shales may, 

 indeed, have been contemporaneous with that of the coral reef close by. 

 The most striking characters of this fauna, as compared with 



that of Padaukpin, are the prevalence of 

 nities™f feuna 1 & lamellibranchs, and the close relationship with 



American forms, especially those belonging to 

 the Hamilton, or middle Devonian group of that country. The 

 occurrence of the almost exclusively American genus Palceoneilo, 

 which, as we will see, flourished also at a much later date in the 

 Shan seas, is the most conspicuous instance of this affinity, but 

 the fauna as a whole bears traces of it, no less than 24 out of the 

 30 species described from Wetwin, being compared by Mr. Cowper 

 Reed with American forms. 1 Indeed it seems to me not at all 

 unlikely that, if the fauna of the Plateau Limestone had not been 

 so completely destroyed, we would find that there was in reality 

 not nearly so close a resemblance with the European Devonian type 

 of fauna as the sporadic occurrence at Padaukpin would indicate. 

 The Wetwin shales are not the only bands of the kind that 

 occur among the limestones of the plateau, 



Other bands of shale. , , . , r , , 



though this particular fauna has not been 



brought to light elsewhere. Indeed, shaly bands may be much 



more frequent than one would suppose, for their outcrops are apt 



to be washed out and filled in with the universal red clay that 



covers the ground. It is therefore only in fresh cuttings cn the 



railway or road that they are likely to be found. At the same 



time sections like that in the Gokteik gorge, where there is a 



1 F. R. Cowper Reed, Pre-Carboniferous Life-Provinces; Records, Oeol. Qurv. Ind., 

 Vol. XL, Pi 1, p. 3i. 



