GENERAL RANGE OF SILURIAN ROCKS IN RUSSIA. 38* 
Although not rich in variety of coralline species, the Lower Silurian rocks of 
ussia are occasionally loaded with numerous individuals of two or three species, of 
w lich the Chatetes Petropolitanus is by far the most abundant ; a coral, which, it is 
important to remark, is also prolific in the lower beds of Norway, and has recently 
been detected in similar strata in North Wales'. Overlying the deposits in which 
the fossils already cited are accumulated is a calcareous band with Pentameri, 
which we consider the representative of that zone which in the British Isles, Scandi- 
navia and North America, contains the Pentamerus obloncjus, to which our P. borealis 
makes a close approach. And just as this band is intermediate between the lower 
and upper groups, so does it contain fossils which range into both (such as the 
Leptcenadepressa), and in it we already find the Catenipora escharoides and one or 
two species of corals of the true Upper Silurian group. 
lhe striking distinctions between the Upper Silurian deposits of the Baltic Isles 
and those lower formations which constitute the mainlands of Sweden on the one 
land and of Russia on the other, have been already so clearly defined, that it is 
unnecessary now to say more, than that through a multitude of corals and many 
typical shells, the Wenlock and Ludlow rocks of England are there very adequately 
represented, the latter even exhibiting the very highest beds of the system. 
We have therefore to repeat, that the Russian palaeozoic strata described in this 
chapter are unquestionably of the same age as those which are termed Silurian in 
otier paits of the world; and that here, as in Scandinavia and the British Isles, 
they are divided into two natural groups, and are overlaid by the Devonian or Old 
Red system of deposits which we are about to describe. 
In concluding this chapter, we may further briefly state, that whilst our present 
observations lefer to the Silurian formations of the Baltic provinces of Russia 
only, we believe, from the descriptions of other authors 2 , that strata of the same 
he has authorized us to state, that among these forms of Cystideae, which are, however, mere internal casts, 
the Sphceronites aurantium is clearly recognisable. The remains seen by M. von Buch are from the 
quarry of Slides Hook, near Haverfordwest, a locality which we formerly described as Lower Silurian. 
(See Silurian System, p. 397.) We are also informed by Captain James, R.E. of the Ordnance Geolo- 
gical Survey of Ireland, that he suspects he has found similar bodies in the Lower Silurian strata of the 
county of Waterford. The Lower Silurian rocks of Scandinavia, Russia and the British Isles are there- 
fore closely bound together through these remarkable fossils. 
■ By Professor Sedgwick. 
* We DOt °" ly trust t0 the Published descriptions of Eiehwald and Pusch, but also to communications 
we have received from Major Blbde and M. Dubois de Montpereux, and to our having seen unquestionable 
i urian species, such as Conularia Sowerbyi and Terebratula plicatella, obtained from these tracts. 
