DE VERNEUIL AND d'aRCHIAC ON RUSSIAN PAL-3E0Z0IC FOSSILS. 99 



forms considerable banks. The Syringopora {Harmodites of Fischer), 

 chietiy represented by the two species S. parallela and S. distans^ 

 is in that form characteristic of the mountain limestone, and widely 

 spread. Catenipora on the other hand, in Russia as elsewhere, is 

 confined to the Silurian rocks, and is there unknown in the lowest 

 beds, but appears towards the termination of the lower series, and 

 is especially abundant in the upper part of the system. The genus 

 Fenestella is common in the carboniferous and Permian systems, 

 and in the Ural furnishes a useful means of distinguishing the car- 

 boniferous from the lower limestones, which are often entirely made 

 up of Stromatopora concentrica and Favosites alveolaris and F, po' 

 lymorpha. It is worthy of remark, that in the Ural Mountains the 

 Devonian system, there developed in massive limestones, contains a 

 number of corals, but in the plains these fossils are rare ; and it is 

 only in the middle of the country and on the banks of the Don near 

 Voroneje that a {esv species, as Aulopora serpens, Favosites spongites, 

 &c., are found. The genus Lithostrotion is represented by four 

 species, viz. L. emarciatum, L. mammillare. L. astroides and L.flori- 

 forme, and is met with throughout in the carboniferous limestone. 



Infusoria and Foraminifera. — Although, if we may judge by their 

 simplicity of organization, it is most probable that these animals 

 existed from the very first introduction of organic life, the altered 

 condition of the ancient rocks in most parts of the world has hitherto 

 prevented remains of this kind from being discovered. No such 

 obstacle however is met with in Russia, where the carboniferous 

 limestones are still in their original condition, and thus they have 

 already furnished several species to naturalists who have examined 

 them under the microscope. In the silex disseminated through the 

 limestones, and in the limestones themselves, M. Ehrenberg has 

 discovered most of these minute animals, and he has already enu- 

 merated seven or eight species, one of which, Borelis sphcei^oidea, 

 appears to differ but little from a recent Italian species. Such mi- 

 nute fossils however, so difficult to perceive and determine, are far 

 less useful in practice than the Fusulina cylindrica, a Foraminife- 

 rous shell common in the upper carboniferous limestone, and espe- 

 cially characteristic of this part of the formation on the Dwina, the 

 Volga, the Kliasma and the Donetz, and in the Ural. 



liadiata* — Various plates and spines found in the carboniferous 

 limestone have till lately been referred to the genus Cidaris; and 

 it is rather singular that Mr. M'Coy and M. Agassiz sliould have 

 been the first to observe that these plates being hexagonal could not 

 have belonged to Cidaris, since in that genua the ambulacral and 

 inter-ambulacral spaces are only composed of two ranges of penta- 

 gonal pieces. From the form of the plates, it is evident that the 

 animal of these carboniferous fossils was provided with several rows 

 of inter-ambulacral pieces, and differed from Cidaris in the same 

 manner as the palaeozoic Echinoderms, called by Dr. Scouler Pa- 

 IcBchinus, differ from the Echinus of a newer period or of the exist- 

 ing seas. Although in Russia we have not found plates in which 

 the form has been well-preserved, we do not doubt that Cidaris 



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