38 GEOLOGICAL MEMOIRS. 



when struck, as is the case with the Orthoceratite limestone, the 

 odour rather resembles that obtained by rubbing two pieces of 

 quartz together. 



2. PalcBontological characters. — In these beds the trilobites appear 

 to be gradually dying out. No new genera are introduced, although 

 all the species are new. These crustaceans are here, as elsewhere, 

 more developed in beds which contain silex than in those entirely 

 made up of carbonate of lime. 



The Cephalopoda are in this group also reduced to a smaller 

 number of species and but few individuals. They also differ from 

 those of the former period. There have not been found amongst 

 them any typical forms named and described in the Silurian rocks of 

 other countries. 



The Brachiopoda, which had been very rare in the earlier de- 

 posits, are here predominant, although the number identical with 

 known forms is very small. Amongst these are Terehratula {Atry- 

 pa) compressa^ T. prisca, Orthis orbicularis ? M. v. Buch has 

 given the name Pentamerus Sieberi to a species closely resembling 

 P. galeatus, and characteristic of this group (F). This Pentamerus 

 is associated generally with a Terebratula which the author calls 

 T. princeps, the geological equivalent of T. Wilsoni, from which 

 however it differs by specific peculiarities. 



There are 40 species of Terebratula in this middle calcareous 

 group of Bohemia, about 10 Spirifers, 5 or 6 species of Leptaena, 

 several of Orthis, and one single Lingula. Most of the Brachiopods 

 occur in a white limestone which forms hills between the villages of 

 Konieprus and Mnienian, and of whose richness in these fossils the 

 author has been aware for some years. It has been erroneously 

 stated that these fossils are from Litten, which is not within the 

 calcareous basin, and is situated at some distance from the true 

 locality. 



In the same calcareous rock are several new genera of Gastero- 

 poda and also Euomphalus sculptus, a species found in England in 

 the three middle groups of the Upper Silurian series. 



In the vertical extension of this group there have been found 

 beds formed almost entirely of encrinital stems ; but the author 

 thinks he can recognise species distinct from Scyphocrinites elegans^ 

 Zenk., which characterises the lower limestone. 



Corals are not rare in the beds now under discussion. Most of 

 the species of Favosites are the same as those in the lower beds ; 

 but they are associated with several species of Retepora^ Hemitrypa, 

 &c., very analogous to those of England. 



The author then describes 27 species of Trilobites from the beds 

 of this group, amongst which he distinguishes 21 exclusively con- 

 fined to them. He considers this fact, combined with the generally 

 distinct character of the species in other countries, as sufficient to 

 justify the separation of the group from the beds below and above it. 



The comparison with the fossils of other countries offers too little 

 that is definite to justify any conclusions being drawn. 



Group G. {Upper Limestone Group.) — 1. Geological characters. 



