42 INFERIOR OOLITE AMMONITES. 



Ammonites which occur in these beds, their insertion here in their sequence will be 

 useful. 



It will be seen that Lioc. opalinum occurs only sparingly, and of small size, in 

 the top of what has generally been called the Gloucestershire Cephalopoda-bed 1 (or 

 rather well up in Bed 16, Haresfield), but that it is most abundant and of largest 

 size (five and a half inches in diameter) in the hard rock above, that is, exactly 

 in the position where Quenstedt states it should come. 2 It is this rock, a foot or 

 so thick, very hard, emitting a metallic ring when struck, that Dr. Wright must 

 have considered to be Inferior Oolite, while placing the beds below in the Upper 

 Lias, because this rock could not in any way be called a "thin band of hard ferru- 

 ginous marl" a description which does apply to the beds below. Dr. Wright's 

 statement seems to mean that Lioc. opalinum occurred in the thin band of marl 

 even so high up as to leave its impression on the rock above, but, as it did not 

 occur in the rock itself, here was the dividing line between the Opalinum- and 

 Murchisonce-zones, and therefore between the Lias and Oolite. The majority, 

 however, and the best developed of my specimens of Lioc. opalinum have been 

 obtained from this hard rock above the so-called " Cephalopoda-bed." The hard 

 rock must, therefore, be considered to belong to the Opalinum-zone, and, by Dr. 

 Wright's system, that means to the Lias. He, however, considered it Inferior 

 Oolite, in which opinion I fancy he would meet with full support. The Opalinum- 

 zone must then be considered to be in the Inferior Oolite and not in the Lias, and 

 the line of division between the Lias and the Oolite must be drawn at any rate 

 lelow this zone. How much higher than Bed 15 the Opalinum-zone may be 

 considered to range, or how much more would have to be placed in the Lias if the 

 zone were to stand part of that formation, is certainly a question not easily 

 to be determined by the very scanty fauna (especially Ammonites) that has been 

 obtained from the beds above. The zone may or may not include the " Sandy 

 Ferruginous " beds, 3 D', and the same may be said of the " Lower Limestone " 

 series, D", but we know that it does not include the Pea-grit proper, which 

 belongs, without doubt, to the Murcltisonce-zone. 



1 The Cephalopoda-bed is considered to be the soft friable marl (beds 17, 18, 19, and perhaps 

 part of 16, section V). Dr. Lycett, ' Cotteswold Hills,' p. 20, says of it, " Its thickness at Haresfield 

 Hill is not more than two feet, its colour is dark or chocolate-like, and it is so little compacted that 

 it may be broken up by the hands alone." 



2 Compare Lycett, ' Cotteswold Hills,' p. 27, and corrigenda, p. 164; also p. 163. 



3 See 'On the Pisolite and Basement-beds of the Inferior Oolite of the Cotteswolds,' by 

 E. Witchell, Esq., E.G.S. 



