ZONE OF AMMONITES MURCIIISON.^. 95 



feet thick. It represents the zone of Jitimonilcs nituiphricsicmHS; this rock is here almost 

 non-fossilifcrons, altliough the eqnivalent bed at Cleeve Hill contains a rich fanna. 



No. 5. The Fimbria bed or Oolite marl, is a cream-coloured mud-stone, not unlike 

 chalk-marl; the dominant shell is Terebratula fimbria, Sow.; it contains likewise 

 Lueina Wrighti, Oppel., Lima punclala, Phil., L. Poiitonis, Lye, Natica Lcc/i/iamp- 

 toiiensis, Lye, Natica adducta, Phil., Mj/tih's pcctimitm. Sow., Asfarfc clrt/atis. Sow., 

 Neriiiaa, sp., Clicmnifzia, sp., and masses of Coral, chiefly T/iamnastraa Mettensis, Edw. 

 This bed was deposited under conditions very different to that of the freestone on which it 

 rests ; as its lower portion is slightly brecciated, and the surface of the freestone on which 

 that breccia was deposited had been for some time exposed to aqueous action and made 

 smooth thereby. The marl measures about seven feet in thickness, and passes upwards into 

 a marly limestone, becoming oolitic in the uppermost layers. This division of the bed is 

 about ten feet thick. The Fimbria bed is a constant feature in the Inferior Oolite of the 

 Cheltenham district, and in the northern and middle Cotteswolds, but is absent in the 

 southern parts of that range. It forms the upper part of the zone of Ammonites MurcJnsonee. 



No. G. The Freestone is a compact light-coloured oolitic limestone ; the uppermost 

 beds are the best for building purposes ; the middle beds are of an inferior quality, and 

 are stained in part with the peroxide of iron ; the lower beds contain large Oolite-grains, 

 and are called "roestone;" the freestone in all is about 110 feet in thickness. 



'The Pea-grit {Zone of Ammonites Miirchisona) Inferior Oolite. 



Ft. 



A. A brown, coarse, rubbly Oolite, full of flattened concretions cemented together by a cal- 



careous matrix. When the blocks weather, the concretions, which resemble flattened 



peas, form a very uneven surface. It contains many fossils in good preservation ... 12 



B. A hard, cream-coloured, pisolitic rock, made up of flattened concretions, with a 



thickness about similar to those in a 10 



c. A coarse, brown, ferruginous rock, composed of large oolitic grains ; it is readily disin- 

 tegrated by the frost, and is of little economical value. About 20 



The Cephalopoda-bed {Zone of Ammonites Jurensis). 



D. A brown marly rock, full of small dark oolitic grains of the hydrate of iron, which are 



strewed in profusion in a calcareous paste. About 2 



d'. a thin seam of yellowish sand H 



E. A dark-gray crystalline limestone, extremely hard, and resembling some beds of the 



Carboniferous limestone ; it is bored in diff'erent places by Fistulana ?, the shells of 



which remain in the excavations 9 



1'. A brown, argillaceous, sandy bed, full of micaceous particles ; passing downwards into 

 fine brown and yellow sands. Thickness unknown. 



G. Upper Lias Clay, of a dark blue colour. Thickness probably IGO 



