456 
The Hon. Mr. Strangways on the 
primitive country. They all agree in consisting of a limestone 
resembling the Pleta, lying on strata of sand and bituminous or 
aluminous clay, slightly differing from those of Russia. The red 
Pleta with ortho-ceratites, may be identified with that of Osmunds- 
berg in Dalecarlia : the yellow containing trilobites, with that of the 
Isle of Gothland ; the entrochites, &c. of Esthonia, with those of 
Scania. In many parts it is covered by floetz trap and floetz 
porphyry. I confess myself unable to trace these formations any 
further. I suspect their existence in the south of Norway, and 
their western boundary must be sought in Scotland and England 5 
in the latter country, the transition limestone, with trilobites and 
orthoceratites, and its accompanying sandy and argillaceous beds 
are the only rocks I know that bear the least resemblance to them.* 
Their southern edges must be looked for along the north of 
Germany, the south of Poland, and Russia. The intermediate 
country of Denmark does not seem to present any trace of them. 
* On comparing a very complete series which I was able to collect of this limestone, 
.with the transition limestone of Longhope, and the environs of May Hill on the north west 
of Gloucester, Professor Buckland has ascertained an agreement in so many minute 
circumstances of the rock itself, as well as of its organic remains, as to feel the most confident 
assurance of their identity, the resemblance is particularly striking in those varieties of the 
limestone which are charged with magnesia, and the chief difference appears to consist in 
the accidental presence of grains of chloritic earth disseminated through some of the strata 
near Petersburg, such grains not being usual in the transition limestone of England. 
This identity being admitted, we may expect to find in the limestone shale and slaty 
sandstones of the English transition series, analogous depositions to the beds of slaty clay 
and siliceous sand that lie beneath the limestone in Russia. 
In several varieties of these latter, this analogy is faithfully maintained, but in the 
greater part of them a want of compactness, either original or resulting from gradual 
decomposition, reduces much of the sandstone to the condition of mere loose sand, whilst 
the argillaceous slates present an appearance of unstratified clay. 
For a detailed account of these transition rocks in England, on which Professor 
Buckland has founded his comparison with those of Russia, see his paper on the districts 
adjoining to the Severn in South Gloucestershire. 
