302 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. [March 25, 



jpriodon, and G. SedgiuicTcii. Among the strata "^hich are asso- 

 ciated with the graptolitic shales here, Cardiola interrupta is met 

 ■with, and it is found elsewhere in Ireland under similar circum- 

 stances*. ]y!r. Jukes, in a note appended to the account of this 

 occurrence of Upper Llandeilo and Caradoc fossils in the county 

 Waterford, notices this association, and seems disposed to refer it to 

 the recurrence of similar conditions and habitats at different Si- 

 lurian periods — a conclusion which the fossil evidence of the Conis- 

 ton mudstones appears strongly to support. 



The occurrence of a rich Graptolite fauna among the Caradoc 

 rocks of Great Britain seems to have its parallel among the Silurian 

 rocks of Bohemia. Barrande places his rich Graptolite fauna towards 

 the top of the Lower Silurian, and among the base of the Upper 

 Silurian rocks ; in the latter the graptolitiferous shales are associated 

 with traps. 



The lower graptolitiferous series rests upon strata QoniaimiigTnnu- 

 clei. In this occur five monoprionidian forms ; and in the base of 

 the Upper Silurians there are twenty species, many of which are also 

 common to the Coniston mudstones. Of these the two diprionidian 

 species D. ixdmeus and D. ovatum (D. folium), and Bastrites pere- 

 grinus, are abundant among the Graptohtes at SkelgiUf- 



In America, also, the richest Graptohte fauna, excepting that of 

 the Quebec group, seems to make its appearance in a series of rocks 

 which, in that country, in part represents the Caradoc formation. 

 These rocks are the Utica slates. They contain many of the forms 

 which are found in the Coniston mudstones, and they seem to be 

 very nearly on the same parallel with these latter rocks t. 



A circumstance of considerable interest in connexion with the 

 fauna and sequence of the Coniston group is the intercalation of the 

 mudstones and their fossils with the grey sandstones which lead up 

 into the cleaved Coniston flags. The occurrence also of O. Sagitta- 

 rius in so high an horizon as the Coniston grits connects these latter 

 with the rest of the Coniston series. 



There are other fossils which are common alike to the Coniston 

 flags and Coniston grits ; but in the grits forms make their appear- 

 ance which have not hitherto been discovered elsewhere. The fossils 

 of these grits have very little affinity with those of the Kendal 

 flags, nor do they exhibit such a facies aswould connect them with the 

 lower members of the Upper Silurian series. Palaeontologically, 

 therefore, this Coniston series of the north-west of England must 

 be looked upon as a continuous group of rocks extending from, and 

 including, the green slates and porphyries to the top of the Coniston 

 grits. 



The physical evidence also leads to the same conclusion. Every- 

 where, as was long ago pointed out by Prof. Sedgwick, there is the 

 same sequence ; there is no overlap, but there is a perfect conforma- 

 bility throughout the whole series. 



* Explanatory notes to sheet 133, p. 19. 



t Graptolites'de Boheme, p. 18. 



X Hall, ' Palaeontology of New York,' vol. i. p. 265, et seq. 



