48 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May G, 



contains some remains described as fishes by Eichwald under the 

 name of Sphagodus obliquus. 



The fifth division forms the summit of the Silurian system of 

 Esthonia, and is composed chiefly of a crystalline limestone, rarely 

 dolomitic, alternating with beds of marl or shale. The remains of 

 fishes now begin to appear frequently, and Pander has recognized in 

 the materials sent to him twenty species, all of which, however, are 

 affirmed by him to be specifically distinct from any Devonian or 

 Old Red forms. 



The finest of these Upper Silurian species is the Cephalaspis 

 verrucosus, Pand. (Thyestes, Eichw.), and with it is found the 

 Onchus Murchisoni, Ag., of the Ludlow rock ; sufficient fragments 

 of the former having been detected to complete the restoration of 

 an almost entire fish. These remains, including numerous scales 

 and also portions of jaws, are now described by M. Pander*. 



One of the most remarkable fossils of this band is the Eurypterus 

 remipes, Dekay, which is abundant in some of the marly beds, and 

 in so admirable a state of preservation as to permit the delineation 

 of all its minutest parts, which Dr. Schrenek will elucidate. 



The most important of the other fossils of this, the highest Silurian 

 zone in Russia, are : Beyrichia tuberculata, Klod., B. Wilckensiana, 

 Jones, Leperditia Baltica, His., L. phaseolus, Klod., Orthoceras 

 imbricatum, 0. bullatum, Sow., Murehisonia cingulata, Trochus 

 helicites, Pterinea reticulata, Grammysia cingulata, His., Lucina 

 (Tellina) prisca, Chonetes striatella, Dalm., Spirigerina prunum, 

 Dalm., S. didyma, Rhynchonella Wilsoni, Sow. (Sil. Syst.), Orthis 

 orbicularis, Sow. (Sil. Syst.), Tentaculites annulatus, His. (?), Cya- 

 thocrinus rvgosus, Mill., Cyathophyllum articulatum, &c. 



These grey beds (so manifestly identical through many of the 

 species of their organic remains with those of the Upper Ludlow 

 rocks) present no ascending passage, as in England, into the super- 

 jacent red or Devonian strata. The latter are not seen in the Isle of 

 Oesel, but appear on the continent, where their junction with the 

 Upper Silurian is evidently transgressive. At Tannekill, to the north 

 of Tellin, for example, the Devonian rocks, consisting of a yellowish- 

 grey coarse-grained grit and bluish marls, are seen to overlie at once 

 the formations Nos. 3, 4 of the preceding Silurian succession, with 

 their characteristic Corals. At Dorpat, Randan, Tellin, and Tonga!, 



* The work of my distinguished friend, M. Pander, has been seen for the 

 first time by me as these pages are printing off. 



Professor Huxley, who has been so obliging as to examine this work, informs 

 me that the Cephalaspis verrucosus {Thyestes, Eichwald) presents a tuberculated 

 ornamentation on the head- and body-scales, which is, as it were, a more regular 

 development of the ornamentation described by Sir P. Egerton as occurring in 

 Cephalaspis ornatus of the uppermost Ludlow rocks (see Quart. Journ. Geol. Soc. 

 vol. xiii. p. 285). These remarkable ichthyolites, of which many genera and 

 species are described, will be alluded to in the new edition of ' Siluria,' when the 

 nature of the singular minute and enigmatical remains, from the Lower Silurian 

 rocks, called " Conodonts" by M. Pander {op. cit. pis. 1, 2, 3, 4) will be discussed. 

 With the highest respect for the author, and the great ability he displays in his 

 works on ichthyolites, I am not yet convinced that these microscopic bodies are 

 portions of the teeth of fishes.— (Oct. 10.— R. T. M.) 



