Dr. Du Riche Preller—Ophiolithic Rocks, W. Liguria. 451 
Upper and Middle Eocene. The division is shown e.g. in the 
interesting superficial section of Mte. Gazo in the Chiaravagna 
Valley (Fig. 2). 
The principal constituents of the pietre verdi of the Voltri group 
are peridotite, lherzolite, serpentine, and euphoditic, amphibolic, 
eclogitic, and garnetiferous rocks. Although in some cases well 
preserved, they conve more generally various stages of alteration, 
schistosity, and decomposition, and are, moreover, so interfolded and 
intermixed both with each other, and with the enclosing, often talcose 
eale-schists that their delimination and subdivision is as difficult as in 
the similar case of the Lanzo Valleys. The peridotitic and serpentinous 
rocks alone are easily distinguished by the dark colour, the rugged 
outlines, and the barrenness of their outcrops, in contrast to the other 
pietre verdi and the cale-schists often covered with abundant 
vegetation. 
Along the coast-road between Pegl and Pra tke headlands exhibit 
outerops of dark, dull serpentine and euphodite with glaucophane, in 
part brecciated and decomposed, alternating with shaly, talcose calc- 
schist which fringes the coast from Sestri to Voltri.2, North of Pegli 
in the Varenna and upper Gorzente Valleys appear lherzolite and 
serpentine with euphodite veins, and north of Pra, as also north of 
Voltri, in the Acquasanta ravine, occur considerable rugged outcrops 
of dark-green and black peridotitic rock, which from their forbidding 
appearance are known as the Scogli Neri and the Scoglio del Diavolo. 
Beyond Voltri a large mass of serpentine continues to Arenzano and 
Cogoleto, where it alternates with peridotitic rock and calc-schist. 
Between Cogoleto and Varazze a large mass of euphodite stretches 
north, while at Varazze the dark-green serpentine shows euphodite 
veins. Thus, the continuous mass of peridotitic and serpentinous 
rocks, with associated euphodite and alternating with calc-schist 
along the littoral, is interrupted only by the calc-schist wedge of 
Voltri and Campoligure previously mentioned. 
Along the eastern margin similar outcrops of enstatitic and diopsitic 
lherzolite, glaucophanic euphodite, and amphibolite appear on the 
western flank of Mte. Gazo, while further north serpentine pre- 
dominates west of Mte. lines again, west of Mte. S. Carlo in the 
Iso Valley a lherzolitic mass exhibits euphodite veins, and lherzolite 
and serpentine also crop out in Mte. Persucco and Mte. Roncasci, 
west of Caffarella. From here extends on both sides of the Apennine 
erest the great euphodite mass of Mte. Lecco, probably connected 
with the similar mass north of Varazze in the south-western part of 
the area. In this, asin the other euphodite masses, the rock varies 
from the well-preserved diallagic to the altered type with saussurite 
and smaragdite, and is often gneissiform, laminated, and schistose. 
In the Olba Valley, north of the Apennine crest, occur considerable 
eclogitic masses, and along the western margin contiguous to the 
' This section is deduced from Rovereto’s more extensive one, op. cit., 
p. 414. 
2 Professor Bonney described some of the coastal rocks between Sestri and 
Pra in *‘ Notes on some Ligurian and Tuscan Serpentines’’: GEOL. MAG., 
May, 1879, p. 362 et seq. 
