Ch. XX.] 



LOWER OOLITE. 



401 



the Middle Oolite, extending inland from 

 Scarborough in a southerly direction. The 

 number of mollusca which it contains is, 

 according to Mr. Etheridge, 106, of which 

 only twenty-three, or 22-| per cent., are 

 common to the Oxford clay proper. Of 

 the twenty Cephalopoda, eight (namely, 

 one of the Sepia family, six species of 

 ammonite, and the Ancyloceras Callovi- 

 ense) are common to the Oxford Clay, giv- 

 ing a proportion of 40 per cent. 



If, on the other hand, we compare the 

 fossils of all kinds in the Kelloway rock, 

 amounting to 151 species, with the fossils 

 of the underlying Lower Oolite, we find 

 that seventy-four pass down into the older 

 rocks, or about 49 per cent. ; or if we con- 

 fine our attention to the mollusca alone of 

 the Kelloway considered as tho base of the 

 Middle Oolite, and compare them with 

 those of the Cornbrash, or the top mem- 

 ber of the Lower Oolite, we find 106 spe- 

 cies in the Kelloway, and 123 in the Corn- 

 brash, and 22 species common to the two, 

 implying a community of 21 per cent, be- 

 tween the two formations. 



Fig. 347. 



LOWER OOLITE. 



Cornbrash and Forest Marble. — The 

 upper division of this series, which is more 

 extensive than the preceding or Middle 

 Oolite, is called in England the Cornbrash. 

 It consists of clays and calcareous sand- 

 stones, which pass downwards into the 

 Forest Marble, an argillaceous limestone, 

 abounding in marine fossils. In some 

 places, as at Bradford, this limestone is. 

 replaced by a mass of clay. The sand- 

 stones of the Forest Marble of Wiltshire 

 are often ripple-marked and filled with 

 fragments of broken shells and pieces of 

 drift-wood, having evidently been formed 

 on a coast. Rippled slabs of fissile oolite 

 are used for roofing, and have been traced 

 over a broad band of country from Brad- 

 26 



r- 1 - 



$& 





K5 



www. 



|J5- 



Belemnites Puzosianus, 



JB. Oicenii, Pierce. 



Oxford Clay, Christian Malford. 



a, a. Projecting processes of the 

 shell or phragmocone. 



&, c. Broken exterior of a coni- 

 cal shell called the phrag- 

 mocone, which is cham- 

 bered within, or composed 

 of a series of shallow con- 

 cave cells pierced by a 

 siphuncle. 



c, d. The gnard or osselet, which 

 is commonly called the 

 belemnite. 



