FROM THE ZONE OF AMMONITES ANGULATUS. 69 



XXV. APPENDIX. 



Note on the Age op the Sutton Stone and Brocastle, &c., Deposits. 



A long and very elaborate essay, by Mr. Charles Moore, F.G.S., has been read before 

 the Geological Society, and published in the ' Quarterly Journal' of that society, with the 

 title, " On Abnormal Conditions of Secondary Deposits when connected with the Somerset- 

 shire and South Wales Coal-Basin, and on the Age of the Satton and Southerndown 

 Series," whicli suggests that it is more or less controversial; but although this is the case, 

 still it has great intrinsic merits. 



Mr. Bristow, F.R.S., read a paper before the Geological Society, which appeared in 

 its ' Quarterly Journal,' " On the Lower Lias or Lias-conglomerate of a part of Glamorgan- 

 shire." Like Mr. Charles Moore's communication, it is very valuable, besides being con- 

 troversial. Lately also Mr. R. Tate, F.G.S., in his essay "On the Fossiliferous Develop- 

 ment of the Zone of Ammonites angulatus, Schlot., in Great Britain," has produced a palseon- 

 tological criticism which refers in one part to the "abnormal deposits" and "the Lias- 

 conglomerate." 



Each of these essays refers to the characters and to the age of the Sutton Stone, whose 

 Madreporaria have been described in this Part. Mr. Bristow considers the Southerndown 

 series of Mr. Tawney^ to be a portion of the Sutton Stone or " Lias-conglomerate," and 

 asserts that Mr. Tawney has made a great error in his section of the sea face of the deposit 

 by giving it too great an elevation. Mr. Bristow also considers the Sutton Stone to be 

 Lower Lias, and that the usual Gryphma incurva occurring in abundance renders his 

 opinion incontrovertible. Mr. Moore, on the contrary, admits the correctness of Mr. 

 Tawney 's section, but considers that insufficient altitude has been given. He considers 

 that, as Ostrea Liassica {0. irregularis) occurs high up in the series as a " zone," and as 

 Ammonites planorbis is wanting, the Sutton Stone is in the " Ostrea division" of the 

 Ammonites planorbis Zone. Mr. Moore places the Brocastle deposit in the Ostrea 

 series. He insists upon the presence of Gryphaa incurva in the Sutton Stone and in 

 the deposit at Brocastle " in abundance," and localizes the deposits in the Lower Lias.^ 



Mr. Tate proves what I had already demonstrated^ — that Mr. Tawney placed the 

 Sutton Stone too low down in the geological scale ; and, after a survey of the beds above 

 the White Lias in Ireland and England, he considers that the Ammonites planorbis Zone is 



' Tawney, 'Quart. Jour. Geol. Soc.,' vol. xxii, p. 91. 



2 A palseontological combination of the forms of the lower part of the Zone of Ammonites planorbis 

 with Gryphcea incurva would indeed be incredible. 



3 P. Martin Duncan, 'Quart. Jour. Geol. Soc.,' Feb., 1867 ; and in the 1st No. of this Part. 



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