GEOLOGICAL POSITION OF THE PENTAMERUS LIMESTONE. 
34* 
fossils, as at Kleine Pungarn and Paggar*. In the limestone at these places we 
could no longer detect the characteristic Orthoceratites and Trilobites before spoken 
of ; but with some species of the lower rocks, such as Spirifer lynx (Eichw.) and 
Terebratula deformata (Eichw.), we also found the Leptcena depressa (Sow.) and 
L. deltoidea (Conrad). These beds indicate a passage into, and form, indeed, part 
of a calcareous band, which ranges by Mustel north of Wissenstein in Esthonia, 
and reappears in the government of Kovno 2 . This band, like that which is in the 
same geological position in Norway, where it is immediately superposed to the chief 
mass of the Lower Silurian rocks, is here, as in that country, characterized by 
containing Pentameri, the Esthonian species being the P. borealis (Eichw 3 .) — a 
shell which approaching very near to it, is, we consider, the equivalent of the P. ob- 
longus of Scandinavia and the British Isles 4 . 
In one tract north-west of Wissenstein, it would appear (from a friendly com- 
munication of M. Pander) that the Pentamerus limestone is underlaid by a course 
of sandstone. In the tract of the government of Kovno, where we observed these 
beds, the upper calcareous strata alone appear through the great mass of overlying 
detritus. Judging from the red colour of the matrix of this detritus, and from 
certain cuttings on the sides of the new road between Tauroggen on the Russian 
frontier and the third post station, we were induced to suspect that the subsoil 
must belong to the Old Red or Devonian rocks. This view was confirmed by the 
relations of those deposits to the Lower Silurian rocks in the government of 
St. Petersburgh. 
The emergence of grey Silurian rocks from beneath a surrounding region ot red 
deposits (due probably to a flexure like that upon the Volkof, p. 30 # ) is even seen 
by the change in the colour of the soil in the neighbourhood of Bublia and Shavli. 
The limestone which gives rise to this superficial aspect is, however, worked at 
Neici and Griis to the west of Shavli (see Map) in the extensive domains of the 
1 The residence of Count O. V. Stackelberg. 
2 This government has recently been separated from that of Vilna. 
3 We had absolutely named and spoken of this shell in print (Proc. Geol. Soc.) as Pentamerus Letticus 
three years ago, but whilst our publication was in progress Professor Eichwald described it as P. borealis. 
1 We owe our knowledge of this extension of the Silurian band in question to M. Pander, who, when 
we visited him at Riga (1841), identified the fossils we had found at Shavli with forms known to him in 
Esthonia. We also learned from this author, that at about forty to fifty versts north of the locality near 
Shavli, where we observed it, this Pentamerus limestone is exposed from west to east throughout a space 
of twenty versts in perfectly horizontal strata. 
