72 LA TOUCHE : GEOLOGY OF NORTHERN SHAN STATES. 



Passing now to the brachiopoda, Schizotreta occurs typically in 



Brachio da ^ e ^ r( ^ ov ' c i an °^ Russia, and the species 



occurring at Sedaw is comparable with S. 

 elliftica Kutorga, the type of the genus. Rafinesquina has a wide 

 distribution in northern Europe and America, and the Sedaw 

 form, R. imbrex, is a typical species of the lower Ordovician in 

 both regions. It is also very widely distributed in the Naung- 

 kangyi beds of the Shan States, occurring both in the lower 

 and upper portion of the series, and at most of the localities 

 from which fossils have been collected. Clitambonites (Orthisina) 

 pyron, to which Mr. Cowper Reed compares the specimen of this 

 genus found at Sedaw, occurs in the Echinosph*rite limestone 

 (lower Llandeilo) of Russia. Porambonites ranges from Ordovician 

 to lower Devonian, but it is most fully represented in the lower 

 Ordovician of Russia and Scandinavia. P. intercedens Pander is 

 the type of the genus. 



It is impossible to give any exact estimate of the thickness of 

 these strata exposed at Sedaw, and indeed it 



minS neSS DOfc det€r " ma 7 be Stated onCe for a11 that this is true 

 for the whole area under description. In very 



few outcrops is the junction of any individual bed with those 

 either over or underlying it visible, and in no single instance that 

 I am aware of is the base and summit of a bed to be seen in one 

 and the same section. No measurements of the thicknesses of 

 strata can therefore be given, as they would only be misleading, 

 and indeed the thickness of even the larger groups varies so 

 greatly from one locality to another that measurements made at 

 any one spot would only have a strictly local value. 



The peculiar beds exposed at Sedaw are, as I have already men- 

 tioned, not found either to the north or south 

 ric£ St ° f Ngwetaung of that place. To the north the beds imme- 

 diately overlying the sandstones of Ngwetaung 

 along the eastern side of the ridge, were found to contain, in a 

 soft yellow marl, fragments of cystideans, namely Cheirocrinus sp., 

 a genus that has a very wide distribution both horizontally and 

 vertically, ranging from the Baltic Provinces to Bohemia and North 

 America, and through the whole Ordovician period ; and a species of 

 Caryocrimis. Specimens of these are very 

 ^onf"^^ 6611 lin " : " numerous in an outcrop in the bed of a stream 

 at the foot of the ridge on the path from 

 Taungkyun to Sibaing (Loc 86, B 5). Thick bands of limestone 



