122 LA TOUCHE : GEOLOGY OF NORTHERN SHAN STATES. 



in the latter country between the Rochester Shale, the equivalent 

 of the stage in which it occurs in Bohemia, and the Helderberg 

 Group, — it appears to me that it would be unsafe to argue too closely 

 from its presence here regarding the relative age of the deposit. More- 

 over, the stratigraphical evidence indicates that there must have been a 

 considerable interval between the period of deposition of theNyaung- 

 baw Limestone and that of the Zebingyi beds ; for not only is a 

 whole formation, the Nam-hsim sandstone, of Wenlock age (which 

 on the Nam-Tu attains a thickness of at least 2,000 feet), almost 

 sntirely absent in the western sections, where the Nyaungbaw and 

 the Zebingyi beds are in contact ; but I have also convinced my- 

 self, having been over the ground several times, that there is a 

 decided unconformity between these two formations. This may be 

 observed in the railway cuttings about a mile below Zebingyi 

 station, and in a small cutting about a quarter of a mile east of 

 Thondaung station, where the Zebingyi beds are actually seen 

 resting upon an eroded surface of the Nyaungbaw Limestone, one 

 of the very few instances I know of where the actual contact of 

 two formations is visible (Plate 9, see also fig. 5, p. 169). 



The Nyaungbaw Limestones appear to cover a very restricted 

 t _ b area. Some patches of them occur among 



the hills north of Maymyo (Loc. 72, C 4), 

 where specimens of Camarocrinus asiaticus were found by Mr. E. A. 

 Gabbett, Executive Engineer in the Public Works Department, in 

 quarrying the stone for the Municipal Water-works Reservoir. 

 Hence they extend at intervals to the north, forming a line of 

 conspicuous ridges near Palin, about 6 miles north of Maymyo, 

 where a few fossils were found in them, including Diplotrypa palin- 

 ensis Reed ; Lingula cf. quadrata Eichwald ; Plectambonites repanda 

 Salter ; and Orthis irravadica Reed. Of these the first and last 

 are new species ; the Diplotrypa differs from that of Sedaw in 

 possessing no acanthopores and in the irregularity of the dia- 

 phragms in the mesopores, and in the former respect resembles Meso- 

 trypa quebecensis Ami and M. discoidea Ulrich. The Orthis is a 

 common Naungkangyi form. Livqula quadrata occurs in the Ordo- 

 vician beds of Russia and the Craighead limestone of Girvan, and 

 I'lcclaiiibonites repanda in the Oidovician of Niti. So far as these 

 fossils go, therefore, the Nyaungbaw Limestone would seem to be- 

 long to a lower horizon than the beds with Labolithus in Bohemia, 

 which correspond to the W enlock and Ludlow of England, or than 



