part 4] jUEASSic ciiiioisroLOGY. 407 



Yet the non -sequences ure not always synchronous in the different 

 sections. 



The main feature of the Watton Bed is the amount of deposit 

 containing forms of Grammoceras-striatulum type, which, how- 

 ever, there is reason to suppose, are redeposited specimens. Yet 

 the mam mass of the Watton Bed is a hardened paper-shale — thin 

 laminfB of ver}^ fine mud, — indicating a slowly-accumulating tranquil 

 deposit. These statements appear to conflict : so does the state- 

 ment about tranquillity with the observation that some ammonites 

 are found more or less on edge, and that fairly large blocks of 

 Tetrarliyncli i a-tJiorncomhiensis Bed have been redeposited in the 

 Watton Bed. 



The reason for supposing that the forms of striatulum type are 

 redeposited are the following :-- At Bothenhampton J. F.Walker 

 found striatulum forms in a brown bed, and a species of later date 

 (^Ammonites c/ermaini) in white stone. The striatulum forms of 

 the Watton Bed show evidence of a yellowish-brown matrix, 

 although the3^are found in a very white lithographic stone. Asso- 

 ciated with the striatulum forms are species of Hammatoceras — one 

 form of the H. insicpie tj^pe found in the rock itself and another 

 (a rare and peculiar form somewhat removed from insigne, but 

 certainly a Hammatoceras) was found on the lower platform loose : 

 the matrix of the Watton Bed, however, is unmistakable. Now, 

 Hammatoceras is of considerably later date than the striatulom 

 forms, as may be seen from the synopsis on p. 401 (Table II). 

 It is presumably of about the same date as the Ammonites 

 germaini quoted by Walker, but is of -pre-Dumortieria age. 

 Therefore, tlie evidence appears to show that the forms of stria- 

 tulum type which are found in Bed 4 are redeposited in strata 

 of Hammatoceras date. 



In the layer above, No. 3, is found evidence of a still later 

 horizon, Dumorfieria. The specimen belongs to a species with 

 coarse, rather distant ribs, and is closel}' allied to Dumortieria 

 nooata S. Buckman (p. 387). But in this layer there is very 

 plain evidence of redeposition apart from the striatulum forms : 

 there is Hildoceras of hifrons type, which is a species some five 

 hemerse earlier than striatulum forms and some eleven hemer^ 

 earlier than Dumortieria ; and there are specimens of Tetra- 

 rliynchia tlionicombieiisis, which is some twenty hemerse earlier 

 than striatulum and some twenty-six earlier than Dumortieria. 



It is evident, then, that the fossils which the Watton Bed yields 

 are not to be trusted as evidence of the date of its deposition. 

 And there is further evidence on this head in the finding of Harpo- 

 ceras ^ft. falciferum {mulgravium) in the top of the bed (p. 388). 

 Therefore, it is only possible to date the bed by the latest fossils 

 which it contains. 



What is, however, of considerable interest is the faunal 



m version 



Harpoceras at the top of the bed. 

 Hildoceras aff. hifrons in layer 3. 

 Grammoceras of striatulum type m layers 4 & 5. 



