- Dr. Du Riche Pretler—Ophiolithic Rocks, E. Liguria. 495 
the upper part to brecciated limestone and diabase, whose repeated 
alternations are followed by a mass of diaspri wedged between diabasic 
breccia, and then by large masses of spheroidal diabase. From Prato, 
which lies in normal sedimentary strata, to Mte. Agugiaia (1,088 m.) 
the outcrops again disclose brecciated alternations with spheroidal 
and variolitic diabase, then a large mass of reddish bastitic peridotite 
which forms the cupola of Campo Rondio, and is surrounded by 
diabase and an outer fringe of argillaceous schist. Diabase is again 
in evidence on Mte. Bregaceto (1,171 m.) and extends to Mte. delle 
Lame (1,804 m.), which, though covered with plantation, exhibits 
that rock on its lower flanks. 
From Mte. delle Lame the crest is reached on Mte. Ajona (1,692 m.), 
on whose comparatively broad and flat surface appears a very hard, 
dark-red, and rusty-coloured peridotitic rock in superposed layers like 
flagstones, with reticular ribs and wrinkles evidently due to atmo- 
spheric denudation. This rock, which is strongly magnetic and extends 
considerably north of the crest, obviously passes to serpentine on the 
southern flank, where serpentinous and limestone breccia appear 
infolded in argillaceous schist. ‘The crest of Mte. Nero towards south~- 
east of Mte. Ajona exhibits the same peridotitic rock passing to 
serpentine, and so does the remarkable outcrop of Pria Borgheise, 
a boss on Prato Molle (1,496 m.), below Mte. Nero, which was first 
noticed by Mazzuoli and, thanks to Professor Cossa’s microscopic 
examination, was recognized as the first example of lherzolite in the 
Ligurian Apennines. East of Mte. Ajona rise Mte. Cantomoro and 
the peak of Mte. Penna, both composed of diabase, which also applies 
to Mte. Scaletta south-west of Mte. Penna. These three mountains 
obviously form a central mass of diabase between the peridotitic and 
serpentinous masses on the west and those of Mte. Pertusio on the 
east. Mte. Scaletta and Mte. Pertusio are separated by the argillaceous 
schist and limestone breccia of Mte. Rocchetta. ‘The semicircular 
- group is completed by Mte. Ghiffi, on whose northern flank appear 
limestone and breccia, the contact of these rocks and the serpentine 
of Mte. Pertusio being exposed in the saddle between the two 
mountains. On the descent from here by Rocca Borzone the hard 
diabasic breccia with associated diaspri appear again, being evidently 
connected with those already noticed above Prato. A notable feature 
of the Mte. Penna group is the absence of superficial outcrops of 
euphodite, though that rock probably occurs in places below the 
surface where the latter is covered with vegetation or detritus, in 
association with diabase and serpentine as it does in the other ophio- 
lithic areas of Eastern Liguria. North of the Mte. Penna group, 
about a dozen ophiolithic, chiefly serpentinous, islands crop out in the 
Trebbia, Aveto, and Nure Valleys, near Bobbio, 8S. Stefano, and 
Ferriere respectively, towards Piacenza in the Po Valley; they are 
obviously a continuation of the Ligurian groups.’ The diabasic masses 
1 J. Mazzuoli, ‘‘ Formazione ofiolitica nella Valle del Penna’’: Boll. R. 
Com. geol., 1884, p. 384 et seq. A. Cossa, ‘‘ Intorno ad alcune roccie della 
Valle del Penna nell’Apennino ligure’’: Rendiconti R. Accad. Lincei, Roma, 
1886, pp. 502 and 643 et seq. Professor Cossa, of Turin, also first examined 
