384 
DESCENT OF THE TCHUSSOYAYA. 
Relations of underlying Silurian Grauwacke to Devonian Limestone on the Serebrianka. 
56 . 
or further down the stream, the calcareous bands expand into highly fractured, 
slaty limestone, which is subordinate to hard sandstone. Up to this point the 
limestones and schists, a and b, may be Silurian ; but at two versts lower down, 
the beds acquiring more regularity (strong-bedded black limestone), we found in 
them several fossils which convinced us that they were of the age of the South 
Devonshire, or Eifel strata. For besides the Leptcena Uralensis and Terebratula 
reticularis, both of which descend into strata which may prove to be of Silurian 
age, we may cite a Clymenia, Cyrtoceratites, closely resembling an Eifel species, 
Strygocephalus Burtini, Orthis striatulus, Terebratula concentrica, with two new spe- 
cies of Spirifer and several corals. 
The beds of limestone, separated from each other by black carbonaceous courses, 
are here overlaid by highly quartzose, flat-bedded grit, which passes into chert, the 
whole undulating at low angles of inclination 1 5° to 20°, and followed by beds 
slightly differing from the above in being sometimes more, sometimes less cherty 
or flinty and carbonaceous. In one spot indeed ( d of woodcut), these calcareous 
rocks, containing corals, assume very much the lithological facies of the Upper 
Silurian rocks of England, in which small calcareous concretions predominate. But 
notwithstanding all convolutions, we were evidently making an ascending section, 
as the prevalent dip was to the west, and the same Terebratula reticularis was more 
abundant in these uppermost beds than in the lower. We came therefore to the 
conclusion, that the fossiliferous portion of the calcareous zone between the Zavod 
of Serebriansk and the river Tchussovaya is Devonian. In descending the latter 
river we met with repeated and rapid undulations, by which these Devonian rocks 
are seen to support true carboniferous limestone of very dissimilar characters. 
Descent of the Tchussovaya from Ust- Serebriansk to Ust-Koiva' 1 . — The same calca- 
1 In Part I. we printed the word Koiva with a C, but the orthoepy to which we have adhered in our 
Map induces us to prefer the K. In partially alluding to this tract in a previous page, 125, we also spoke 
of the loss of certain sketches, which having since been recovered, the illustrations, pp. 386, 387, 388, are 
taken from them. 
