Vol. 54.] COKALLIAN^ KOCKS OF UP WARE. 613 



to the E-ag and oolite is at present dependent on the interpretation 

 placed on the field-section near the well. At first sight it was 

 natural to suppose that the Elsworth Rock formed the base of the 

 Upware Corallian, and that the marl and white rubbly limestone 

 above it represented the lowest part of the oolite. The Elsworth 

 E,ock comes to the surface a short distance south of the well, while 

 the higher beds of oolite and the E,ag in the Southern Quarry rise 

 towards the south, the last-named being lost at the surface some 

 50 yards from the southern end of the quarry. With the slight 

 dip there apparent a considerable thickness of oolite might have 

 cropped out, bringing its basement-bed to the surface in the neigh- 

 bourhood of the field-section and the well. Indeed, but for the 

 white limestone and its fauna in this field-section, probably no one 

 would hesitate to adopt the simpler explanation that the Elsworth 

 Eock comes below the base of the Upware oolite, a considerable 

 thickness of the latter having cropped out and been lost at the surface, 

 an explanation more closely in accordance with preconceived ideas 

 of the position of the Elsworth Eock. Even as it is, the presence 

 above of a fauna not found at Upware lower in the oolite than its 

 highest beds might be explained away on the ground that the rock 

 in which it occurs is not an oolite, and that, under conditions 

 slightly different from that of the oolitic deposit, the Eag-f auna might 

 have come down somewhat lower. This view does not commend 

 itself to the present writer. We may urge against it : (1) that the 

 limitation of a large number of the fossils of this overlying limestone 

 to the Eag and highest oolite is absolute at Upware ; (2) that, as 

 already stated, there is no sign of a break ; (3) that evidence from 

 dip is of no value here, for it has been shown that the beds undulate, 

 and that the higher Corallian comes on again about | mile farther 

 south ; (4) that the white limestone here resembles more closely 

 the Eag than the oolite, and has every appearance of a detrital 

 origin, from degradation of the reef, and that, if so, it must neces- 

 sarily occur above the oolite and not at its base ; (5) that, if of detrital 

 origin, its fauna could not be earlier than that of the reef from 

 which it is derived ; (6) that if the oolite had cropped out and been 

 denuded, bringing its basement-bed to the surface, then this spot 

 would have been well within the area of oolitic deposit and there 

 would be no apparent reason for the occurrence here of a limestone 

 of a different type ; (7) that in the well at High Fen Earm there is 

 no sign of a non-oolitic limestone or of the approach of a ' Eag ' 

 fauna, but there are indications of the proximity of clay ; (8) that 

 the ' Eag ' fauna, well represented in the top of this section by reef- 

 corals, lamellibranchs, and Cidaris^ seems to belong to somewhat 

 shallow-water conditions, and probably for that reason is not found 

 low down in the oolite. 



It may be suggested that possibly the white limestone here is not 

 conformable to the underlying beds. JSTo such unconformity is visible ; 

 there seems to be a complete passage upwards : a regular gradation 

 from the continuous crystalline layers with Thecosmilia to the higher 

 broken layers with Thamnastrcea and Isastrcea. If there were a 

 break at the base of this white limestone, none could be suggested 



