part 4] juKASsic cheo:n^ologt. 417 



recurred in the same area after the lapse of some fifteen to twenty 

 hemerae, so there is ground for surmising that the same phenomenon 

 occurred at Watton ClifE after the lapse of some ten to fifteen 

 hemerae. But the two beds of presumed different dates at Watton 

 Cliff have coalesced. Yet coalescence of unlike deposits separated 

 by more than twenty hemerie in time is well known ; rarer, of 

 necessity, is the coalescence of two like deposits of different dates, 

 because the chances against it are greater : but it is known, and 

 was commented upon in mj'^ last paper.i Possibl}^ other cases of 

 such coalescence ha\'e been overlooked, because they were not 

 understood. If only such coalescence of the Burton and Watton 

 white beds had taken place, it v,'ould have provided a problem and 

 a crojD of ingenious surmises before it was understood. And there 

 is just the possibility that such coalescence did occur — somewhere 

 out to sea, in the neighbourhood of the axis of the Weymouth 

 Anticline. 



The third theorj'' seems to have the greatest Aveight of proba- 

 bility in its favour ; but, at present, that is all that can be said 

 for it. If correct, it makes the Watton Bed contemporaneous, so 

 far as its earliest part is concerned, with the ^Ye-falciferum paper- 

 shales of the North Gloucestershire Whitbian, and, so far as its 

 later part is concerned, contemporaneous with the top layer of the 

 Bothenhampton section, with the Yeovilian Sands of Cole, near 

 Bruton (Somerset), and with the middle part of the Gloucestershire 

 Cephalopod-Bed. It will be noticed that at present there is no 

 ammonite evidence for any of the hemerae between Hammatoceras 

 and sfriafifhnu — in descending order: dispansum, sfruchmanni, 

 pedicum, eseri. Tliej have not been found at Bothenhampton nor 

 in the Western Cliffs — at the former place towards the top of the 

 Junction -Bed there is, consequently, a gap of four hemerae; at 

 Doghus and Down Cliffs, between the Junction-Bed and the over- 

 lying Down-Cliff Clay, there is a gap of five hemerae ; at Thorn- 

 combe Beacon there is a gap of six hemerae. At Shoot's Lane, 

 Symondsbury (Dorset), evidence for esfiri has been found — 

 Ilaugia fascigera'^ (now JEsericei-as).^ 



Stress has been laid on stratal repetition and coalescence, because 

 this may possibly explain some of the Continental deposits which 

 are puzzling, on account of inclusion in the same matrix of species 

 of very widely different dates. 



In the Ked Ammonite-Limestone of Lombardy are species of 

 various dates, from Domerian through Whitbian to Yeovilian, with 

 certain notable omissions. The dates of the species are fairly 

 obvious, and the deposit possibl}^ represents a continuit}- of 

 like conditions with erosions. But were the gaps — the portions 



] I, 9, p. 86. 2 i^ 5^ p^ 57. 



^ I, 8. pi. clxxxii. Since this was written, examination of Mr. Jackson's 

 finds g-ives evidence for fauna of eseri and pedicum (or strucTcmanni hemera, 

 perhaps) in the Western Cliifs. Such finds are always possible, and do not 

 invalidate my statements ; they stand good for many exposures of the Junc- 

 tion-Bed of the Western Cliffs. 



