158 Dr. CO. S. Du Riche Preller—Pretre Verdi. 
and more especially the predominantly Liassic, age of the cale-schist 
formation, including in the same the pietre verdi as associated rocks. 
He thus assimilated the age of that formation and that of the schistes 
lustrés in accordance with Bertrand’s views, with which he is 
thoroughly imbued and which, since Bertrand’s death, have been 
upheld and even carried considerably further by Termier. 
Franchi’s memoirs and his evolution from the Archean to the 
Mesozoic led to a controversy as interesting as it was vigorous and 
protracted, between Zaccagna and himself, not as to the facts, which 
were not in dispute, but as to the interpretation of the same. ‘'o 
Franchi’s contention Zaccagna' opposed, on stratigraphical grounds, 
his own explanation that the fossiliferous calcareous and dolomitic 
deposits occur in eroded gaps and as squeezed wedges (przsicature) 
in the crystalline cale-schists, in which they were infolded by 
dynamic action, in certain cases by displacements due to local 
overthrusts, and that as such they are quite distinct from the true 
cale-schists, whose pre-Palwozoic age he therefore strenuously 
reaffirmed.2? In the result Professor Taramelli, of Pavia, and 
Professor Parona, of Turin, as referees appointed by the Geological 
Survey, recommended, in their reasoned report of 1911,° that for the 
purposes of the new large-scale map 1: 100,000 of the Piémontese 
Alps, Franchi’s interpretation, as being, in their view, more con- 
vincing and up-to-date, should be adopted, but with the explicit and 
judicious reservation that the question cannot be considered settled 
but remains open; that at a lower horizon there may be cale-schists 
conjunction with Mattirolo, who supported Zaccagna’s interpretation. Franchi 
published in Boll. R. Com. geol., 1909, p. 252, a forty-page reference of the 
literature on the crystalline schists from Gastaldi (1871) downwards. 
The principal localities which yielded Triassic and Liassic fossils in the 
calcareous and dolomitic masses of the calc-schist horizon are the Grana, 
Narbone, Maira, Elva, and Varaita Valleys in Southern Piémont; Chianoc in 
the lower, and Rocca d’Ambin, Gad d’Oulx, and Bardonecchia in the upper 
Susa Valley; Villeneuve in the upper Aosta Valley, and the Col du Petit 
St. Bernard, all in Northern Piémont. The fossils, most of which were 
determined by Professor Di Stefano and Professor Canavari, include, among 
others, Radiolaria, Belemnites, Arietites, Crinoids, Hncrinus, Pleurotomaria, 
Avicula, Corallari, Gyropelle, Pentacrinus, Phylloceras, etc. 
1D. Zaceagna, ‘‘Osservazioni sugli ultimi lavori intorno alle Alpi 
Occidentali’’: Boll. Com. geol., 1901, pp. 4, 129; 1902, p. 149; 1903, 
p. 297. 
2 Zaccagna’s interpretation agrees with Professor Bonney’s view that nothing 
is more common in the Alps than Jurassic and Triassic wedges in the crystalline 
schists. ‘‘ Mesozoic Rocks and Crystalline Schists in the Lepontine Alps’’: 
Q.J.G.S., 1894, p. 285; also ibid., p. 277. Baretti (Studi Gran Paradiso, 
etc., 1876-7) also considered the French calc-schists the upper and the 
Piémontese calc-schists as the lower crystalline formation. 
3'T. Taramelli and C. F. Parona, ‘‘ Relazione sull’et& da assegnarsi alla 
zona delle pietre verdi nella Carta geol. delle Alpi Occidentali’’: Boll. R. Com. 
geol., 1911, pp. x-xxiv. The controversy between Franchi and Zaccagna 
turned more especially on the great calc-schist area extending from the 
Gesso Valley in Southern Piémont parallel to the Franco-Italian frontier to 
the Susa and Aosta Valleys towards Monte Rosa. ‘The smaller, isolated 
area of Courmayeur, running parallel to Mont Blanc, was recognized as 
Liassic and Triassic, and was, therefore, not in dispute. 
