GEOLOGICAL MEMOIRS. 



members, and endeavours to explain away the discordance by the 

 supposed effects of denudation and subsequent change of position 

 (p. 19). The two higher members of H rest conformably on the 

 lower one. They are entirely unfossiliferous, with the exception of 

 a few fucoidal impressions on the surfaces of the sandstones which 

 characterize the middle division. 



Of the rich fauna contained in these two zones in Bohemia, 

 amounting altogether to 254 species, a very small number only are 

 known to Britain. The fish-remains referred to the genera Cocco- 

 steus, Asterolepis, Gompholepis, and Ctenacanthus, which occur in g 1, 

 are all absent from British Silurian strata. Coccosteus first appears 

 in zone F, but the species does not pass up. Hence vertebrate genera 

 which characterize our Old Red Sandstone series, in Bohemia occur 

 many hundred feet lower down in the geological scale. 



As regards the Invertebrata the general results are given in the 

 following Table : — 



General Table of the Vertical Distribution of the Fossils in the 

 Stages G and H. 



Genera 



and 

 species. 



E. 



F. 



G. 



H. 



Species common to 



Total 

 number 

 of recur- 

 rent 

 species 

 from 



f- 



f 



f 



Ai 



Ji' 



h^ 



g^kg\ 



g^kg\ 



g^ &gs. 



G&H. 



G-H. 



Fishes 







4 

 49 

 39 

 10 

 16 

 29 

 17 



6 













"3 



5 



2 

 1 

 7 

 1 



2 



"i 



2 



2 



1 

 3 

 

 



2 

 4 



2 

 



2 



4 



1 



"2 

 4 



2 







2 



1 

 



"7 

 13 

 6 

 2 

 12 

 6 

 3 



Crustacea 



Cephalopoda . . . 



Pteropoda 



Gasteropoda ... 

 Brachiopoda ... 



Acephala 



Eadiata 



3 



15 



1 



2 

 8 

 1 



18 

 7 

 3 

 5 



20 

 3 



5 

 8 

 3 

 3 

 8 

 8 

 4 



2 

 62 



1 



5 

 5 

 1 



2 

 5 

 2 



... 





2 

 4 



















30 



56 



170 



39 



79 



15 







21 



9 



15 



11 



49 



303 



The total number of species in the two stages G and H is there- 

 fore 303, which, deducting 49 for recurrent species, leaves 254 for 

 the entire fauna. Of the 15 species which occur in H, there are 

 only 4, namely, Orthoceras equisetum, Barr., Avicula consanguis, 

 Barr., A. rarissima, Barr., and Cardiola retrostriata, Y. Buch, which 

 are not contained in G. The latter, however, occurs in E. 



bQ species pass up from stage E, and 30 from stage E. Of these 

 86 species, 12 are common to both these stages, leaving 74 species, or 

 one-third nearly, as common to the two upper and two lower zones 

 of the third fauna. 



g 1 and g 3 are undistinguishable lithologicaUy, but are easily re- 

 cognized by the difference in their palaeontologieal contents, all 



