SILURIAN SYSTEM : LOWER NAMHSIM STAGE. 



133 



casts of Orthonota are not uncommon at other localities in these 

 sandstones, though they are so imperfect that it is hopeless to 

 attempt to make out their specific characters. Of the two species 

 of Proetus, both of which are very imperfect, the one designated 

 a by Mr. Cowper Reed bears some resemblance to the Wenlock 

 species Pr. Fletcheri Salter, while sp. f3 differs from this in having 

 a more oval, pointed, and deeply lobed glabella. The genus has 

 a wide range, from Ordovician to Devonian. Regarding Cheirurus 

 inexpectans Mr. Reed says : — 



" There is only one specimen of this peculiar little trilobite. Its generic 

 position seems to be in Cheirurus. The very forward position of the eyes 

 and of the first lateral furrows of the glabella, the lobation of the glabella, 

 and general course of the facial sutures, suggest an alliance with Ch. vinculum 

 Barr., but the latter is an Ordovician species." (Op. cit., p. 137.) 



It is somewhat remarkable that, although this patch ot sand- 

 stone occurs close to the line of cliffs 

 t Re L tions t with Pla " bordering the western edge of the plateau, 

 along the top of which the Plateau Lime- 

 stones are found extending in an unbroken line from north to south, 

 no trace of it has been detected at the base of these limestones, 

 which, throughout the whole distance, appear to rest directly upon 

 the upper Naungkangyi beds. The sandstones must either have 

 been deposited over a very limited area at this locality, or they 

 must have been subjected to denudation before the limestones 

 were formed. 



The Namhsim Sandstones next appear along the northern edge 

 of the plateau, between Kalagwe and the valley 

 p] Northem edge of 0 f ^ Nam-panhse at Pa-mon. They are not, 

 however, seen actually below the limestone of the 

 plateau, but occur as outliers on the spurs of the hills, formed of Chaung- 

 Magyi rocks, immediately to the north. It is possible that their 

 non-appearance beneath the limestones here is due to faulting along 

 the base of the hills, but it may also be caused by an overlap of 

 the limestones. The only fossils obtained from this area, on the 

 spur north of Nainhsu-hka and south-east of Nan-yok (C 2), were 

 poorly preserved casts of a gastropod, which Mr. Cowper Reed 

 considers, with some hesitation, to be a Pyawmphalus, comparable 

 with Trochus helicites Sowerby, from the upper Ludlow and lower 



