J30 LATOUCHE: GEOLOGY OF NORTHERN SHAN STATES. 



on either side of the route taken : neither Mr. Datta, therefore, or 

 the present -writer, who carried out that traverse, became aware 

 of the existence of any rocks between the Naungkangyi group and 

 what were then named by us the Zebingyi beds, at the base of the 

 Plateau Limestone or ' Maymyo beds ' of our first reports. No 

 mention of this formation, consequently, appears in our respective 

 accounts of the geology, published in the General Report of the 

 Geological Survey of India, 1899-1900 (pp. 74, 122). It was not 

 until the next field season that I discovered a patch of felspathic 

 sandstones, with coarse conglomerates at their base, on the crest of 

 the Memauk spur overlooking the village of Aunglok (Loc. 47, B 4), 

 at the extreme edge of the western scarp, and found in the sand- 

 stones specimens of fossils, which I recognised as belonging to the 

 well-known Silurian genus Orthonota, with fragments of trilobites. 

 Later on in the same season I found, on the south side of the 

 gorge of the Namhsim at Hkyawngtwang (E 2), about 13 miles 

 above its conflux with the Nam-Tu, a series of sandstones, reaching 

 a thickness of over 1,200 feet, intervening between the purple beds 

 at the top of the Naungkangyis exposed in the bed of the river 

 and the base of the Plateau Limestone crowning the scarp. To 

 these beds I gave the name of Namhsim Sandstones, and afterwards 

 found that in the Nam-Tu valley they attain a thickness of at 

 least 2,000 feet, and extend for a long distance along the banks 

 of that river. 



As in the ca3e of the Naungkangyi group, the fossils that were 

 collected from the whole of the Namhsim forma- 

 Two divisions rocog- tion were sent to Mr. Cowper Reed before the 

 stratigraphical features of the beds had been 

 studied in detail, and it was not until his Memoir had been published that 

 it was found that at least two fairly well-marked divisions could be de- 

 tected ; one consisting of the Namhsim Sandstones, as understood at 

 first, now described as the lower division, and the other of a much 

 thinner band of marly beds with hard limestones, which appeared to 

 have a close connection with the overlying Zebingyi beds, and was 

 described along with the latter in my report on the first traverse 

 (Gen. Rep. 1899-1900, pp. 79, 88). Since that report was written, 

 however, it has been found that the marly beds have a very much 

 wider distribution than the Zebingyi graptolite-bearing beds, and 

 that their association with the Namhsim Sandstones is equally close. 

 Moreover, some of the fossils from this band have been described 



