CORALLIAN BEDS. 329 



seem to be one continuous formation, and to be bound together 

 by many forms in common.^ Further south in Huntingdonshire, 

 Cambridgeshire, Bedfordshire, and Buckinghamshire, the Corallian 

 series is, as a rule, absent ; and it is not until we approach Wheatley 

 in Oxfordshire that the series is again persistently developed. The 

 Calcareous grit has, however, been observed at Houghton Hill, 

 between Huntingdon and St. Ives, and at Papworth St. Edward, 

 south-east of Huntingdon. This absence, which causes the Kime- 

 ridge and Oxford Clays to come directly together, by no means 

 proves any unconformity, for most calcareous rocks occur in great 

 lenticular masses. Prof. Sedgwick has observed that the large 

 area of fen-land, occupying the Bedford Level and a considerable 

 portion of Lincolnshire, rests on a deposit of clay of great but 

 unknown thickness. The lower portion of this deposit belongs 

 to the Oxford Clay, and the higher portion to the Kimeridge Clay ; 

 and there is no indication of any break between these formations. 

 For this great ' Pelolithic ' formation, as it has been termed. Prof. 

 Seeley proposed the name of Fen Clay in 1861.^ The Sub- 

 Wealden exploration at Battle proved the absence of Corallian 

 rock-beds ; but Prof. J. F. Blake has suggested that the ' Supra- 

 coralline beds ' may be represented by 390 feet of strata, and the 

 Corallian beds by 90 feet.^ (See Fig. 31, p. 202.) 



Actual representatives of the Corallian series are met with in 

 what has been called the " Cambridge reef," at the hamlet of 

 Upware, between Ely and Cambridge. Here north of the Inn 

 termed " Five miles from anywhere " are two quarries in the 

 Upware Limestone. The rock in the southern pit is regarded by 

 Messrs. Blake and Hudleston as representing the Coral Rag (zone 

 of Cidaris florigemma), and the northern pit as representing a lower 

 horizon, the Coralline Oolite.^ (See Fig. 68.) 



The researches of Professors Sedgwick and Seeley have shown 

 that at Elsworth, near St. Ives, dark-blue iron-shot limestone about 

 14 feet in thickness occurs near the top of the Oxford Clay. (See 

 Fig. 68.) It contains Ammonites veriebralis, A. perar?)iatus, etc. 

 Also at St. Ives a rock termed the Red Rock of St. Ives, which 

 immediately overlies fossiliferous Oxford Clay, has yielded Pecten 

 fihrosus, Ostrea gregaria, Cidaris florigemma, etc. The rocks of 

 Elsworth and St. Ives are sometimes grouped with the " Lower 

 Calcareous Grit;" they probably represent portions of the Corallian 

 Series of other parts of England. 



Prof. Seeley has observed that the Corallian Beds are replaced in 

 parts of Huntingdonshire, Cambridgeshire, etc., by a clay which is 

 well seen in the cuttings on the Bedford and Luton Railway near 

 Ampthill, where the Oxford and Kimeridge Clays are displayed 

 below and above it. This clay he terms the Ampthill Clay, and it 



^ J. F. Blake, Q.J. xxxi. 216 ; see also Hudleston, P. Geol. Assoc, v. 409. 

 ^ Geologist, iv. 552. 



^ P. Geol. Assoc, vii. 358. See also Topley, Geol. Wealcl, p. 44. 

 * G. Mag. 1878, p. 90; Q. J. xxxiii. 313. See also H. Keeping, G. Mag. 

 1868, p. 273 ; and T. G. Bonney, Cambridgeshire Geology, p. 19. 



