65 



Just so is it in Gloucestershire. A ferruginous oolitic stone 

 resting on a thick bed of sand there forms the base of the oolitic 

 rock, and, as in the so-named Cephalopoda bed at Frocester, some 

 liassic forms of Ammonites were found, it was even proposed by 

 Dr. Wright to allocate this bed with the Lias. 



Now although these two beds, the one in Dorsetshire and the 

 other in Gloucestershire, are both charged with Ammonites of 

 which several species are common to both, I hope to show that they 

 are upwards of a hundred feet apart, the former being near the top 

 of the Inferior Oolite, and the latter so close upon the Lias as to be 

 classed with it. 



So strong, however, was the belief in the identity of these two 

 Cephalopoda beds that up to a certain period all writers described 

 them as situate on the same horizon, and they are so mapped by 

 the Ordnance Survey. Nay, further, we have examined collections 

 of fossils from Bradford Abbas labelled as from Lias. 



To show how confidently geologists spoke upon this matter we 

 extract the following notes from the Journal of the Geological 

 Society for February, 1877 : 



" Every student of the geology of the Cotteswolds has recognised 

 a band at the base of the Inferior Oolite under the name of the 

 'Cephalopoda bed,' so named from the important list of Ammonites, 

 Nautili, and Belemnites which it has been found to contain. 



"To quote from Mr. Hull's 'Memoir on the Geology of the 

 Country around Cheltenham,' l This bed had been long known to 

 geologists as " the ammonite bed ; " but the ammonites were sup- 

 posed characteristic of the Inferior Oolite, and its true importance 

 was overlooked. Dr. Wright, however, found that the species were 

 identical with specimens from the Upper Lias of Whitby, in York- 

 shire. About the same time the work of M. D'Orbigny made its 

 appearance, wherein nearly all the cephalopoda from the ammonite 

 bed are figured and described as " Toarcien? or Upper Lias forms* 

 while even in our own district several of the species were known 

 to be characteristic of the Upper Lias Shale ' (p. 26). 



" Mr. Hull refers to a paper by Dr. Wright in the ' Proceedings of 

 the Geological Society,' vol. xii., in support of the view that the 

 Cotteswold Cephalopoda bed belongs to the Upper Lias and not to 

 the Inferior Oolite, and, further, that the learned Doctor had traced 

 it to the Dorsetshire coast ; and, indeed, in this very paper we find 

 the following remarks upon sections at Half-way House and Brad- 

 I 



