DORSET-SOMERSET DISTRICT. 35 
Comparison of the Dorsetshire and Yorkshire Coasts. 
There is, perhaps, no portion of the Inferior Oolite throughout England which 
is so well illustrated_as the Parkinsoni-zone of Burton Bradstock Cliff, even down 
to very minute details, and it is, of course, all the better for not being inflated 
with too much sedimentary matter. As this is the first glimpse of the Inferior 
Oolite in England, for one coming from the south it might perhaps produce an 
exaggerated notion of the importance of the Parkinsoni-zone. 
One cannot help reflecting on the marvellous contrast presented by the section 
of the Inferior Oolite on the Yorkshire coast. Setting aside the enormous 
difference of physical development, we have in the Nerinea-bed of the Yorkshire 
Dogger a fine development of the Murchisone-zone, and this is indeed the only bed 
of the Inferior Oolite which can be regarded as rich in Gasteropoda in that county. 
But owing to the difference of facies even the Murchisone-bed of Burton Bradstock 
Cliff has not much more resemblance to the Yorkshire Dogger than the.beds of 
the Parkinsoni-zone have. It has many Ammonites and no Nerinzwas, whereas the 
Yorkshire Dogger has many Nerinzas and hardly any Ammonites. If we carry 
the comparison a step higher we find the Cephalopoda of the Humphriesianus- or 
coronaten-zone abundant in certain portions of the Scarborough Limestone, 
whereas in Burton Bradstock Cliff this zone is aborted, or so overshadowed by the 
lower part of the Parkinsoni-zone as to produce no impression. Again, on the 
Yorkshire coast there is no paleontological representative of the Parkinsoni-zone, 
so that in all respects the contrast is most complete. 
In every respect, therefore, the marine beds of the Inferior Oolite on the 
Yorkshire Coast differ surprisingly from those of Dorsetshire. Yet despite this 
difference the relative position of the life zones is always the same so far as the 
Cephalopoda afford the means for comparison. It remains to be seen how far this 
holds good for the Gasteropoda. The contrast between the species of Gasteropoda 
in our Lower and Upper Divisions is exceedingly marked throughout the Dorset 
District, where the abundance and excellent preservation of the Gasteropoda admit 
of the fact being proved to demonstration. Possibly the difference may be shown 
to a certain extent in the Cotteswold District (No. 2), but less clearly, I think, in 
the Yorkshire District (No. 4). 
Reverting once more to the Parkinsoni-zone in Burton Bradstock Cliff, it seems 
to me that the Cotteswold divisions of the Ragstone are to a certain extent pre- 
figured in this exposure. Making due allowance for geographical distance and 
difference of facies, I think that P, corresponds in the main to the Upper Trigonia 
Grit, though here fortunately the matrix is quite of a different character, hence 
lithologically there is no resemblance. Moreover, Rhynchonella spinosa does not 
