ford Abbas, which we quote, as showing that Dr. Wright had at this time identified the Dorset Cephalopoda-bed with the one in Gloucestershire.
"Between Yeovil and Sherborne" the "Cephalopoda-bed is well developed and extensively exposed; and at the Halfway House its relations to the Sands below, and the Limestone of the Inferior Oolite above, may be satisfactorily made out. Here it contains a great many large Ammonites, Nautili, and Belemnites,—as
|
Ammonites dorsetensis, Wright. |
Belemnites breviformis, Voltz. |
"Section VI.—At Bradford Abbas, near Yeovil, Dorsetshire.
"Inferior Oolite.
- "a. Coarse, hard, brown ragstone, slightly oolitic, very irregularly bedded, and containing few fossils: about
20
b and c. Absent.
"Cephalopoda-bed.
- "d. A coarse, brown, oolitic ragstone, composed in part of hard, calcareous, sandy layers, grey and brown, and having softer marly sandy seams running through the rock; it breaks with an uncertain fracture, and sometimes has a flinty hardness: the ragstones are speckled with dark brown flattened oolitic grains of hydrate of iron, and contain many fossils: about
26"[1]
It was then clearly Dr. Wright's view (in which he was, indeed, both preceded and followed by other geologists) that the Dorset Cephalopoda-bed was identical with that of Gloucestershire; and indeed we have seen fossils from the Bradford bed just described labelled as from Upper Lias.
Mr. Strickland, in 1850, considered the ironshot oolite of Dundry the equivalent of the Cephalopoda-bed of the Haresfield Hill. He says, "A few miles to the south the Pisolite disappears and is replaced near Painswick and at Haresfield Hill by strata containing ferruginous oolitic grains in a brown paste. This is the precise equivalent of the well-known oolite of Dundry, near Bristol, which may be recognized as far off as Bridport, on the Dorset coast"[2].
Now this view was quoted by Dr. Wright in a paper published in the 'Quarterly Journal' for 1860, only to be dissented from; for he says of the above, "a comparison, however, of the species of Ammonites and other shells collected in these different localities shows that, besides a similarity in lithological structure, there is nothing in common between the strata"[3]; and he accounts for the appearances by supposing that the Ammonites-Murchisonæ zone, by thinning out, has brought the zone of Ammonites Humphresianus into close relation with the sands of the Upper Lias[3].
