BARRANDE ON THE TRILOBITES OF BOHEMIA. 3? 



of bivalves of the genus Cardium resembling those described by- 

 Count Miinster from Elbersreuth. 



Of Zoophytes the number of species in Bohemia is 44 ?, and there- 

 fore less considerable than those of England, which amount to 65 ; 

 but the same genera are represented (Favosites, Cyathophyllum, Ca- 

 tenipora^ &c.). Most of these are found in the middle of group (E). 



Graptolites ludensis, G. convolutus, and some other species are 

 found chiefly in the nodules. In England they characterise the Lower 

 Ludlow rocks. 



On the whole it appears, that of the English fossils represented in 

 Bohemia, including the corals, the greatest proportion belong to the 

 Wenlock formation, and the smallest proportion to the Lower Ludlow. 

 If however the corals are excluded, the proportions are reversed. 



The group (E) of Bohemia might be considered as representing 

 an epoch corresponding to that during which were formed the 

 English beds extending from the Wenlock shale to the base of the 

 Aymestry limestone, provided the identical species were sufficiently 

 characteristic. Since however they can hardly be considered so, it 

 is necessary to obtain some more definite knowledge before abso- 

 lutely determining the question. To the evidence afforded by the 

 moUusks the author then adds some new indications furnished by 

 the Trilobites. These do not indeed give any forms that are iden- 

 tical in the two countries of Bohemia and Great Britain ; but there 

 are certain analogies, which however seem hardly sufficiently im- 

 portant to deserve being quoted here, and are admitted by the au- 

 thor to be too vague to enable him to establish the comparison of 

 the groups; the materials not including specific identity, and merely 

 a similarity of generic form. 



The author concludes that his group (E) belongs to a palaeozoic pe- 

 riod, different, so far as Bohemia is concerned, both from that which 

 preceded and from those which followed. It does not appear, how- 

 ever, that it can be identified with any subdivision of the Silurian series 

 in other countries ; while, on the other hand, it seems to represent 

 several groups of Upper Silurian rocks as developed in the British 

 Islands. 



Group F. {Middle Calcareous Group.) — Geological characters. — 

 There is no unconformability between the beds of this and the 

 preceding group, nor can they be accurately distinguished by litho- 

 logical character, although there are unequivocal marks of their 

 belonging to a different period, even without the evidence of fossils. 

 These are derived from the presence of silex, which, as has been 

 stated, is not found in the beds of group E. The silex appears in 

 two conditions; sometimes distributed through the rock, and alter- 

 ing its colour and cohesion, but sometimes detached and in cherty 

 nodules. 



The thickness of the different beds is inconsiderable, varying 

 from 4 inches to about 16. The thickness of the formation varies, 

 but sometimes amounts to 300 or 350 feet. 



The colour is, on the whole, different from that of the lower beds, 

 being more grey or whitish, and instead of giving out a fetid odour 



