HIND : CARBONIFEROUS ROCKS OF THE PENNINE SYSTEM. 423 
thus hindering the deposit of the non-detrital but organic 
limestone, which went on uninterruptedly for a long period 
in the area occupied by the southern type of rocks. 
(6) That the distribution of fossils shows most emphatically that 
the fauna of the Carboniferous Limestone of the southern 
t^-pe of rocks is identical with the fauna of the Great Scar 
Limestone and Yoredale series of the northern type. Hence 
the Yoredale series are the homotaxial equivalents of the 
upper part of the Carboniferous Limestone massif " of 
the southern type, and do not in any sense overlie it. The 
comparative thickness of the Great Scar Limestone plus 
the Y'oredale series and the mass of limestone further south 
further corroborates this view. 
(c) That the detrital deposits of shales, dark limestones, and 
quartz-grits which overlie the massif of limestone in the 
southern area are not the equivalents of the Y^oredale series ; 
that this deposit is extremely local and lenticular, and that 
the boundaries of this lenticle can be fairly accurately mapped 
by measured sections, and that the fauna contained in 
these beds is entirely different from that found in the lime- 
stone massif below, and also from that of the Y^oredale series 
of the northern type. 
(d) That many Genera and species of Carboniferous fossils which 
occur low down in the Carboniferous rocks of Scotland 
appear for the first time at higher and higher horizons 
as the beds pass south, demonstrating a migration south- 
ward, and indicating a passage south of similar conditions 
of environment. 
The evidence for these theses is given at length in a paper by 
Mr. Howe and myself, published in the Q. J. Geol. Soc., Vol. LYH, 
1901, and much of it need not be repeated here, but I propose to briefly 
review the chief stratigraphical and paleontological facts on which 
these views are based. 
The southern type of Carboniferous rocks is well seen in the 
periclinal mass of limestone which occupies parts of North Stafford- 
