•A20 ME. s. s. BUCKiiAX OX [vol. Ixxviii, 



Dorset— Somerset evidence of these intervening strata swept away ; 

 land where now is sea, with coalescence instead of separation 

 of the two White Beds. Then we might be examining a rock of 

 white matrix obtained some miles off the Dorset coast which would 

 23uzzle us, because it showed in a homogeneous deposit AYhitbian 

 and Yesulian ammonites. Griven sufficient destruction of evidence, 

 and we might be long in arriving at the solution — erosion, stratal 

 repetition, and then coalescence. Yet such, I think, is the 

 explanation of sundry Continental deposits, and also of the Watton 

 Bed itself : stratal repetition for the Yeovilian deposit and coales- 

 cence with a like AYhitbian deposit — some of the intervening 

 strata, of different lithic composition, being deposited in the 

 Junction-Bed of the Western Cliffs and elsewhere. 



The subject of stratal repetition and coalescence must receive 

 further attention at another time. 



lY. The White Bed or Buetox Beadstock. 



The likeness of the Watton Bed to that which I described as 

 found at Burton Bradstock naturally atti-acted attention.^ That 

 bed is in Bridport Sands and also connected with faulting. 

 Accordingly, in the autunan of 1919, I j)aid another visit to 

 Burton. The first blow of the hammer fortunately hit a block 

 disclosing examples of the same latesulcate ' Garantiana' as that 

 which I mentioned before.- It is not properly a ' Garantiana ' ; 

 but it is a well-known form of the niortense bed of Louse Hill,-^ 

 the Astarfe or Rotten Bed^ which lies above the Irony Bed. A 

 fine-ribbed Perisphinctid was also obtained. 



Subsequent labour, however, proved unproductive of more 

 evidence for date. But a Garanfiana-like form and a Peri- 

 sphinctid in this bed are sufficient to show that, like as these two 

 lithographic strata are in composition, yet they are of widely 

 different dates — the Watton Bed is pre-Bridport Sands, the Burton 

 Bed is on the border-line of Bajocian-Yesuhan. not only post- 

 Bridport Sands, but subsequent to the early and middle Inferior 

 Oolite. What is interestincr. however, is that the same fine muddv 

 sedimentary conditions must have obtained at these two different 

 dates : but, in the Burton case, it is only by the accident of faulting 

 that a fragment of the later deposit has been preserved ; in the 

 Watton-Cliff case the accident of faulting has doubtless preserved 

 the southern extension of the Bed, although that must be buried 

 at a steep angle some 300 feet below Watton Cliff. What has 

 been preserved is the unfaulted part which lies practically hori- 

 zontal in the cliff-face, in position between ^Middle Lias and basal 

 Bridport Sands. 



1 I, 5, p. 69. 2 I 5^ pp_ 7o_7i. 



^ I, 5, p. 71. [Tlie Louse-Hill species has, since this was written, been 

 fibred and named Hlaiciceras platyrryinvm (I, 8. pi. ccxl).^ 

 ^ L 3, p. 488, Section \1. Bed 3. 



