Noticeti of Memoirs. 321 



The fossils, generally speaking, have too wide a range to determine 

 exact horizons in the Upper Greensand, but Mr. Jukes-Browne 

 points out to me that Cytherea plana, which occurs as a phosphatic 

 cast in the nodule-bed, favours the idea of erosion to below the 

 Chert Beds, for he has not observed it from any higher horizon. 



In the Memoir on the Isle of Purbeck (pp. 161, 162) I referred 

 to the general consensus of opinion that there had been some slight 

 erosion of the Upper Greensand before the deposition of the Chloritic 

 Marl, and gave some instances, but I know of no other case in which, 

 the evidence is so strong or where the erosion appears to have been 

 so great as at Mupe Bay. That it was strictly local is proved by 

 the fact that in Lulworth Cove to the west, and in Warbarrow Bay 

 to the east, the sequence is normal, and the Chloritic Marl resumes 

 its normal thickness of 3 to 4 feet. It is unfortunate that the 

 existence of a fault introduces a doubt how far the incompleteness 

 of the sequence should be attributed to contemporaneous erosion and 

 how far to subsequent movement. While accepting the evidence 

 that there was erosion, perhaps considerable, of the Upper Green- 

 sand, I am disposed to call in the aid of the fault at the top as well 

 as at the bottom of the cliff, to account for some of the missing beds. 



My thanks are due to Mr. Hill for giving me the opportunity of 

 making this correction, and for supplying much of the material on 

 which it is founded. 



IsTOTIGES OIF I!vCE3yCOH^S- 



I. — Origin of the Ancient Crystalline Eocks. — Dr. Frank 

 Dawson Adams gives an account of the excursion to the Pyrenees 

 in connection with the Eighth International Geological Congress 

 (Journ. Geol., 1901, ix, pp. 28-46). The object of the excursionists 

 was to examine, under the leadership of Professor Lacroix, certain 

 intrusive granite masses, which have not only intensely altered 

 the strata through which they pierce but which have produced 

 a wholesale transformation of the sedimentary rocks in question 

 into granite, the granite now occupying the space formerly occupied 

 by the sediments. The districts examined were Aix-les-thermes, 

 L'Etang de I'Estagnet, L'Etang de Baxouillade, Cirque de Camp 

 Ras, Foix, Arignac, Cabre, Vicdessos, Sem, Massat, Bagneres-de- 

 Bigorre, Pouzac, Payole, Cirque d'Arbisson, and Bareges. While 

 recognizing that the excursion was merely a rapid traverse of 

 a district which has received detailed attention from the French 

 petrographers. Dr. Adams sums up as follows : " While the 

 transfusion of a certain amount of material into the limestones 

 along the immediate contact of the intrusions and also a solution 

 of the limestone to a limited extent in certain cases seems highly 

 probable ; the wholesale transformation of limestone into diorite, or 

 of shale into gneiss and granite, which has been described in the 

 case of these contact zones of the Pyrenees, is as yet very far indeed 

 from being proved." 



DECADE IV. VOL. VIII. — NO. VII. 21 



