REVIEW OF THE PERMIAN FOSSILS. 
207 
Among the shells of the ancient formations, the Brachiopods are those to which, 
in common with other practical geologists, we attach the greatest importance ; 
and it is by their evidences that we are best enabled to trace the close connexion 
between the Carboniferous and Permian systems. Ten out of the thirty Permian 
species are common to the two systems, whilst the genera Productus and Spirifer, 
both characteristic of the carboniferous epoch, are continued throughout the Per- 
mian deposits ; the first offering six, the second eight species. All the Permian 
Pioducti are very spinous, and the prominent species is the P. horridus (Sow.), 
(P. aculeatus (Schloth.). Two only of this genus are ornamented with regular 
longitudinal striae, viz. the P. Cancrini (nob.) and P. Leplayi (nob.), the first of 
which has a very singular distribution. Occurring profusely through the Permian 
strata of Russia, and serving there as an infallible mark of their age, it is com- 
pletely wanting in the corresponding deposits of Western Europe, but is found in 
one well-known locality of carboniferous limestone at Vise in Belgium l . 
The Spirifers of the Permian system, being all plaited, have much analogy with 
those of the inferior strata: two species appear to be common to this and the car- 
boniferous series, one of which, however, referred by us to the S. hystericus, is still 
doubtful. 
The Orthis, one of the earliest forms of Brachiopods, and which we have shown 
to be so eminently characteristic of the first or Silurian period, decreases in the 
number of its species as it ranges through the Devonian and Carboniferous zones, 
and in the Permian it has but three representatives, one of which occurs in Russia 
and two in Germany. 
The small genus Clionetes (Fischer), the importance of which is chiefly due 
to the wide distribution of one of its species, the C. sarcinulata ( Lepteena lata, 
V. Buch), may be said, in its European distribution, to rise from the Silurian into 
the Carboniferous system ; and if our views respecting the gypsiferous tracts near 
Bachmuth be correct, into Permian deposits also. It is so abundant in the 
Ludlow rocks (Upper Silurian) of England, as to be one of the best types of that 
formation, and in Sweden it seems to occur in beds of the same age. In the 
palseozoic rocks of Great Britain and Belgium, indeed, it continues to the Car- 
boniferous series inclusive ; whilst in Russia, being entirely absent in the Silurian 
and Devonian systems, it appears for the first time in the Carboniferous, and 
more abundantly than in the corresponding deposits of the west ! This fact, though 
1 See De Koninck. Descrip. Foss. Belg. p. 179, pi. 9. f. 3. 1842. 
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