566 TRAIS'SACTIOXS OF SECTION C. 



It was tliere suprgested that the Bristol area ■would probably yield the best results 

 in any attempt to establish a zonal succession in the Lower Carboniferous rocks, 

 and that the corals and brachiopods would yield the most reliable information in 

 this respect. 



How thoroughly these suggestions have been justified is proved by the admir- 

 able results recently obtained by Dr. Vaughan in the Bristol area ; and the time 

 seems ripe for comparing these results with those obtained by the writer in the 

 northern district. 



Four broad divisions were originally suggested for the north. In the above 

 table an attempt is made to establish more detailed subdivisions, and a comparison 

 is instituted with the zones adopted by Dr. Vaughan for the Bristol area. 



The chief conclusion to be drawn from a comparison of the succession in the 

 two areas seems to be that while the general succession of species found in 

 the northern district is the same as in the Bristol area, some of the zonal forms 

 adopted as most characteristic for the Bristol area are either absent or repre- 

 sented by rare or obscure examples in the north, and certainly would not be 

 chosen as typical subdivisions for that district. 



In this table, therefore, the specific names given to the sub-zones in the Bristol 

 area are omitted, to avoid confusion, and the species most characteristic of the 

 northern zones placed in a corresponding column. It will be seen that, as far as 

 the upper and lower zones are concerned, the index fossils are the same; but as 

 regards the Zaphrentis zone, the almost complete absence of this characteristic 

 fossil of the Bristol area from the northern district renders another index 

 necessary. 



Again, although the beds characterised by Michelinia megastoma and Caninia 

 c'jlindrica undoubtedly represent the Syringothyris zone of Bristol, the beds in 

 the north are not characterised by Syringothyris Ictminosa. The same remark 

 applies to the zone of Productus semireticulatus, which is seldom in the north a 

 characteristic fossil at this horizon. On the other hand, if we take assemblages of 

 fossils at any particular horizon, we can correlate the beds in the two areas with 

 some confidence. The accompanying table giving the general results so far 

 arrived at must be taken as a provisional correlation of the two areas only. 



Among the chief points of interest brought out by a study of the faunal suc- 

 cession in the north are (1) the detection of faults in the limestones otherwise 

 obscure ; (2) the oscillations of land, producing shallow-water conditions in cer- 

 tain areas in late Tournaisian and early Vis(5an times, resulting in the absence of 

 the Lithostrotion basaltiforme and Michelinia beds in the Shap andRavenstonedale 

 districts, and the substitution of the Ashfell beds ; (-3) the presence of a land- 

 surface in the Ingleborough district in late Tournaisian times, on which fresh- 

 water deposits containing the remains of Paluclina were laid down ; (4) the 

 dolomitic character of the Tournaisian limestones and the marked silicification of 

 the fossils they contain at certain horizons, especially at the base of the Vis^an. 



Many interesting features occur, with regard to the palfeontological aspect of 

 the succession, which will be found to emphasise the facts and conclusions recently 

 brought forward by Dr. Vaughan for the Bristol district, although on the whole 

 there appears to be an acceleration of the Brachiopod on the Coral fauna in the north. 

 In conclusion, attention may be called to the presence of a fresh-water Gasteropod 

 fauna at the base of the Carboniferous at Horton in Ribblesdale ; the earliest 

 occurrence of freshwater Gasteropoda previously recorded in Europe being near 

 the base of the Jurassic rocks in the lower Oolites. 



Beport on Life-zones in the P>ritish Carboniferous Hocks. 

 See Reports, p. .302. 



Refort on the Fannal Succession in the Carhoniferoiis Limestone of the 

 South-west of England. — See Reports, p. 292. 



