Dr. Fourtau—Echinid Fawna of the Neogene. 355 
the Dora Baltea Valley; and (c) the great longitudinal subsidence 
zone south to north along the eastern margin of the Maira—Dora 
massif contiguous to the Po Valley. ‘his subsidence or flexure zone, 
bordering on the Pliocene sea, probably extended along the base of 
the Lanzo—Iyrea—Val Sesia area and thence to the region of the lakes, 
thus constituting the zonal flexure or settling zone consequent upon 
the raising of the Alps in Hocene—Miocene times.! 
Such is, in my view, the consecutive operation of causes and 
effects which produced the phenomenal masses and groups of eruptive 
rocks, their intimate association with the crystalline sedimentary 
formations, and the alignment and configuration of the Piémontese 
Alps of the present day. In their infinite variety they offer both 
geologically and petrologically an inexhaustible field of fruitful and 
fascinating study, and more especially does this apply to the pietre 
verdi, which Gastaldi rightly described as the great ‘‘ magnesian 
zone”, and whose elusive complexity ever reveals new problems 
without apparent finality.’ 
V.—On ree Ecurnip Fauna or THE Nrocenrt Formations. 
By R. FourtTAU, Member of the Egyptian Institute. 
HAVE just finished the revision of the Neogene Kchinids of 
Egypt preserved in the collections of the Cairo Geological 
Museum. Before the publication of this work, which will form 
the fourth fascicule of the Catalogue of the Fossil Invertebrates of 
Egypt, it has seemed to me that it might be useful to consider 
the fauna as a whole, drawing from it some conclusions as to the 
paleobiology y of the Neogene seas of Egypt. I wish further to 
ascertain i the Echinids of this region can be of some aid as 
regards the stratigraphical divisions, and in synchronizing these 
with the divisions already established in the other regions of the 
‘Neogene basin of the Mediterranean. 
The materials which I had before me for study were, in the main, 
collected by the late Mr. Barron in the Miocene region situated 
between Cairo and the Isthmus of Suez, and also in South-West 
Sinai. Those obtained by Dr. W. F. Hume in the Gebel Zeit area 
and by Dr. John Ball at Gebel Tanka, and in the neighbourhood 
of the mining region of Um Bogma (Sinai), have supplied valuable 
information, to which must be added interesting specimens collected 
by Mr. H. T. Ferrar at Mogara (Libyan Desert), by Mr. Hillman 
from the neighbourhood of Siwa Oasis, by Mr. J. Couyat-Barthoux 
in the Isthmus of Suez area, by A. E. Pachundaki and by myself 
in the neighbourhood of Mersa Matru on the Mediterranean coast of 
Egypt, 185 miles west of Alexandria. I have been able to identify 
1 Vide my previous paper, ‘‘ The Moraine Walls and Lake Basins of Northern 
Tialy,,”” GEOL. MAG., September, 1915, p. 409. 
“ The peculiar liability of the whole Italian peninsula to geological changes _ 
by eruptive and seismitic phenomena, past and present, was aptly emphasized 
by Professor A. Issel, of Genoa, the present President of the Geological Survey 
Department. Asked when the geological map of Italy, begun fifty years ago, 
would be finished, he replied: ‘‘ like Penelope’s web, never.’’ 
