74 On the Silurian Bocks of Bohemia, and 



tinguished by fossils peculiar to it, and distinct from those of 

 the underlying limestone. The middle limestone (/) is, for 

 the most part thin-bedded ; but at Karlstein and other places 

 it assumes a nodular or concretionary structure ; even then, 

 however, it only partially contains the thinnest films of shale 

 between the beds of limestone, and is usually a hard sub- 

 crystalline united congei'ies of thin sti'ata, having a thick- 

 ness of 300 or 400 feet, the colours of which vary from whitish 

 to light grey, and reddish, and occasionally even to blackish 

 tints. Its chief fossils are Brachiopods and Trilobites, and 

 of the former, I may enumerate Terebratula princcps, (Barr.), 

 and its associates ; T. Wilsoni, with Pentamenes, Sperifer, 

 Leptsena, &c. 



The upper limestone is more compact and thick-bedded, 

 and is of about the same thickness as that beneath it. In a 

 ti'ausverse section, which passes from the deep gorge of St 

 Iwan to Hostin, as in a few other places, this rock is seen to 

 be overlaid by brown-grey shale, very slightly micaceous, 

 alternating witli a few courses of very thin-bedded psammite, 

 and very impure limestone. This upper band is distinguished 

 by a few Trilobites only, one of which is the well-known 

 Phacops Hausmanni. In his " Notice Preliminaire,'^ M. Ba- 

 rande has compared these three stages of calcareous strata 

 with the upper Silurian subdivision, as given in my original 

 work ; and has ably pointed out, that although agreeing on 

 the whole with the upper Silurian of the British isles, the 

 Bohemian division is characterised by local peculiarities in 

 the distribution of the fauna. This observation of so good 

 an observer is well worthy of notice. So far from invali- 

 dating the conclusions at which I arrived twelve years ago, 

 when I published my first Synopsis of the Silurian system,* 

 it confirms them in the strongest manner. I then, and in 

 every subsequent publication, specially requested geologists 

 to consider my s/i6-divisions of upper, middle, and lower 

 Ludlow, and upper and lower Wenlock, as mere local British 

 examples, which, even in my own country, were not minera- 

 logically nor zoologically traceable for any great distance. 



* See Philosophical Magazine, Londou, June 1835. 



