44 WILMORE : THE STRUCTURE OF SOME CRAVEN LIMESTONES. 
crystalline character and some fine-grained sediments have 
become masses of semi-crystalline limestones. There are gra- 
dational types between these two extremes. 
It thus seems that we have the coming in of the change to 
the northern type of Lower Carboniferous deposits, already 
shown in the eastern part of the Lower Craven area. Not only 
is there a marked change in the character of the limestone, but, 
as might be expected, there is a change in the fauna. Instead 
of the abundant Rhynconella {pleurodon, pugnus, acuminata), 
Spirifera {hisulcata, glabra, lineata, striata), with Amplexus coral- 
loides and Lithostrotion, Cyathophyllum, we get more of those 
forms which are common to the Pendleside Series, e.g., Athyris 
ambigua, Orthis Michelini, Productus scabriculus, and P. semi- 
reticularis, with an exceedingly abundant development of 
Syringopora (three species), and of Zaphrentis {Enniskilleni, &c.). 
The strata under consideration, with the succeeding forma- 
tions — Pendleside Series, Millstone Grits, and Lower Coal 
Measures afford an excellent illustration of Lord Avebury's 
principle. His experiments in mountain building showed that 
when a series of formations are thrown into a common mass 
of folds, the lower strata show most folding, with the sharpest 
dip, &c. This may well be seen by tracing the beds from the 
middle of the Clitheroe anticlinal through Pendle to Nelson. 
It is similarh- seen when passing from Thornton through 
the Carlton synclinal and the Lothersdale anticlinal to the 
next synclinal of Reedshaw Moss. 
There is thus extensive folding and faulting seen amongst 
the Sedimentary Limestones of the complex anticlinal (and the 
same holds for the small, sharp Lothersdale anticlinal), but it 
seems obvious that there would be some difficulty in accommodat- 
ing the thickened beds of " massive " shell, &c., deposits to such 
a system of internal folding. And in this obvious difficulty 
it seems there may be an explanation of at least one type of 
, reef-knoll. It is important to notice that known faults ac- 
company three out of four of the knoll-masses of Downham 
in such a way as to suggest that faulting has some connection 
with the actual form of these knolls. 
