58 SECTIONS OF THE OKA AND ZUCHA — MTZENSK AND BIELEF. 
In the cliffs at this place are scales of fishes, and at its base we found the Area 
Oreliana, which is characteristic of the highest stratum at Orel and of the middle 
beds at Ottrada. This fact seemed to indicate very clearly, that the general incli- 
nation was to the north, and that in proceeding from south to north, we were 
ascending in the series of strata. 
In travelling from Mtzensk to Bielef, the grotesque concretionary rocks, (often 
covered unconformably by ferruginous sandstone of a much younger age) sink 
gradually under other Devonian strata, in which argillaceous marl, occasionally 
almost a pipe-clay, rarely green and much more frequently yellowish, alternate 
with impure, light yellow, sandy limestone, passing into sandstone, with pisolitic 
beds similar to those of Ottrada. At the station of Budevich, the Terebratula 
Livonica (V. Buch), and T. ventilabrum (Phill.), are grouped with ichthyolites ; and 
from Piscavadi, to near Bielef, an occasional Orthoceratite may be detected. 
At Bielef the precipitous bank of the Oka under the town is interesting, in 
showing marly strata reposing upon the uppermost bed of the grotesque lime- 
stone, which at Mtzensk forms the top of the cliff. As this stratum is here on the 
level of the Oka, it is thus probable (however imperceptible the inclination of the 
strata may be) that the beds have actually dipped to the north more than 100 feet 
in the space of about forty-five miles ; the cliff at Mtzensk having a height of about 
seventy feet, and allowance also being made for the descent of the Oka between 
the two places. 
At the convent of Jabrim, four versts north of Bielef, yellowish, marly and 
earthy limestone prevails, and afterwards the yellow-coloured rocks gradually 
disappear and are succeeded by cream- and white-coloured marls. At Jabrim we 
collected Orthoceratites vermicularis (nob.), Terebratula pleheia (Sow.), with Cythe- 
rinae and casts of Modiola and Nucula. 
Between Bielef and Lichvin we first met with fossils which showed an approach to 
the Carboniferous system ; for the Orthoceratites vermicularis is there associated with 
the Cirrus acutus (Sow.), which, though generally considered a carboniferous fossil, 
occurs also in unquestionable Devonian rocks at Wilmar on the Lahn (Nassau). 
At Kipet we discovered thin calcareous flagstones charged with fishes. In the 
bed of the little brook, blueish, yellow and bright green spotted marls and clays are 
overlaid by brown, hard, flag- like limestones, from three to four inches thick, 
containing Holoptychii. These are covered by yellowish marl and marlstone, and 
a thin course of dark blue, calcareous flagstone, charged with Serpula omphalodes, 
Terebratula plebeia, Modiola, with Orthoceratites and CytherinEe. The strata in 
