380 Reports and Proceedings — 



have been exposed in making railway-cuttings. These were described 

 by the author. The beds usually assigned to the Ehaetic consist of 

 Lower Ehastio — greyish or greenish marls ; Middle or Avicula-con- 

 torta series; and Upper Ehgetic (white Lias), a series of variable 

 shales and light-coloured limestones. The author pointed out that in 

 the Nottinghamshire district there is always a clear line of division, 

 and sometimes indications of erosion between the Avicula- contort a 

 series and the so-called Lower Khgetic beds, while the latter graduate 

 down uninterruptedly into the Upper Keuper Marls. Further, they 

 are practically unfossiliferous, while in the other series there is 

 evidence of marine life and the remains of a fauna ranging upwards 

 into the Lias. Hence the author proposed to class these Lower 

 Ehjetics with the Trias, and regard the RliEctic series as commencing 

 with the base of the Avicula-contorta group. 



5. " On the Silurian and Cambrian Strata of the Baltic provinces 

 of Eussia, as compared with those of Scandinavia and the British 

 Islands." By Dr. F. Schmidt. Communicated by Dr. H. Woodward, 

 F.E.S., F.G.S. 



The Cambrian and Silurian strata in question are found stretching 

 over an area 400 miles long by 80 miles wide. The country occu- 

 pied by these strata is a nearly uniform plain covered by glacial 

 deposits, but sections are presented by the sea-cliffs, which are from 

 90 to 150 feet high. The strata consist mainly of marls and lime- 

 stones, arenaceous deposits being rare, and they form a continuous 

 series from the base of the Cambrian to the top of the Silurian, the 

 whole of these strata being in conformable succession and unconform- 

 ably overlain by the Devonian. Although the representative of the 

 Cambrian or Primordial Silurian contains neither Paradoxides nor 

 Olenus, nor, indeed, any Trilobites whatever, but only Lingulidee and 

 Graptolites, yet its stratigraphical position leaves no doubt as to its 

 age. The Lower Silurian or Ordovician is the richest of the divi- 

 sions, the strata of this age forming a perfectly continuous series. 

 The author divides these beds into the stages B, C, D, E, and F, 

 several of which are divisible into substages. Of the stage B the 

 lowest bed, 1 to 10 feet thick, consists of the Glauconite-bands con- 

 taining the casts of Foraminifera described by Ehrenberg, which 

 correspond to the Ceratopyge stage of the Scandinavian geologists. 

 Above this, and closely connected with it, is the Glauconite-limestone, 

 from 12 to 40 feet thick. Next comes the famous Orthis-lim.estone, 

 a thin bed with a very interesting fauna, corresponding to that of 

 the Phyllograptus-schists. The author's beds C, D, E, and F can be 

 paralleled with the strata of Scandinavia, but have no exact repre- 

 sentatives in the British Islands. The stage E appears to represent 

 the Bala of England or the Trenton of North America. Although 

 there is no stratigraphical break, there is a marked pal^eontological 

 division between the Upper and the Lower Silurian, there being no 

 strata of intermediate age represented. The Upper Silurian is 

 divided by the author into the stages G, H, I, K, which can be 

 exactly correlated with the strata of Scandinavia. The stages G, H 

 do not appear to have precise representatives in the British Islands, 



