356 MB. J. E. MARK ON LIMESTONE-KNOLLS IN [Aug. 1 899, 



anyone who has had much experience in the field among limestone- 

 rocks knows that ' discontinuous distribution " often means only- 

 discontinuity in the area from which fossils have been collected, 

 I believe it to be so in this case, and the existence of the thin white 

 limestone, which has yielded few fossils, but was no doubt entirely 

 composed of organisms, and occupies the position of the Keisley 

 Limestone elsewhere, must be t^ken into account. 



Mr. Reed's views further necessitate a very limited distribution 

 for his ' stations ' of the Keisley Limestone fauna. For the Keisley 

 station 2 or 3 miles at most can be given, unless it is supposed to 

 have extended in a long linear strip at right angles to the present 

 outcrop. Moreover, similar cases of apparent discontinuous dis- 

 tribution occur in other areas under identical conditions, that is, 

 in each case in areas wherein the rocks have undergone erogenic 

 movements. Mr. Reed, it is true, suggests that ' the fact that 

 the limestone in each of these outposts or stations has 

 suffered so much mechanical disturbance may, perhaps, be in the 

 main attributable to its reef-like nature and mode of occurrence, 

 as a local thickening of an elsewhere thin band of rock.' As a 

 result of observation, I should infer that a thin limestone is much 

 more likely to be subjected to such disturbance than one which is 

 locally thickened. I have commented upon Mr. Reed's views at 

 some length, because, if correct, they negative the value of the 

 Keisley Limestone as bearing upon my opinions regarding knoll- 

 structure, for I have maintained elsewhere that the Keisley Lime- 

 stone is ' a block of the neighbouring strata squeezed up and 

 displaced.' This view Mr. Reed curtly dismisses ^ as ' utterly unten- 

 able when we ascertain the unique facies of the fauna and its 

 dissimilarity to that of any other British beds.' I do not see why it 

 is untenable : the view that I have taken accords with observations 

 along other parts of the Coniston Limestone outcrop (which I am not 

 aware that Mr. Reed has examined in detail); that view is as stated 

 above, and I fail to see any difficulty in supposing a deposit to yield 

 abundant fossils in one locality, and not in others. It is a matter 

 of constant occurrence. 



At Millom the outcrops of the Coniston Limestone show knoll- 

 structure, and the dips are very conflicting. At Hillbank there is 

 evidence that the beds are thrown into a series of broken overfolds, 

 with subsequent formation of haematite along the fault-planes. An 

 interesting feature of this section is that, although lithologically 

 similar to the Keisley Limestone, the beds are apparently un- 

 fossiliferous 



At High Haulme, near Dalton-in-Furness, there is a remarkable 

 disposition of the strata or one of the members of the Coniston 

 Limestone Series. They occur in three bands, separated by inter- 

 vening depressions. Each ot these bands is divided by subsidiary 

 depressions into knolls, the limestone in each knoll striking 

 obliquely to the general trend of the bands. It is possible that the 



Quart. Journ. Geol. Soc. toI. liii (1897) p. 101. 



