198 DR. THOMAS STERRY HUNT ON THE 
of outerop, portions of tertiary ophiolites are not mixed and confounded with others of the 
pre-paleozoic period.” These supposed tertiary ophiolites “have a very great resemblance 
to those of the eocene of eastern Liguria, and present moreover a large development of 
of the rocks which Issel has designated as amphimorphic ($ 92.) Thus, near Pietra 
Lavezzara, for example, ophicalcites are exploited which are precisely like the green 
marbles of Levanto. In this same locality, moreover argillites, having the aspect of 
those of the eocene appear to dip beneath the ophiolites.” In support of the belief that 
these seemingly tertiary ophiolites are really eozoic, however, we are told that their outcrops 
present lines of continuity, connecting these serpentines with those of which the eozoic 
origin is undoubted. We have seen ( 41) that Prof. Bonney in his studies of the serpen- 
tines of Italy fails to remark any distinction between the serpentines thus separated by 
the Italian geologists, since he describes as similar both in mineralogical characters and in 
geognostical relations, the ophiolites lying to the west and those lying to the east of the 
meridian of Genoa. I shall further on have occasion to refer to my own observations of 
some of these localities. 
§ 89. The older school of Italian geologists, as already noticed, supposed the serpen- 
tines to have been erupted, like basalts, at different geological periods, and applied this 
view not only those which are evidently included among eozoic rocks, but also to those 
which rise among the tertiary deposits. The study of the ophiolitic masses of eastern 
Liguria and of Tuscany, induced the earlier geologists, like Savi, Pilla and Pareto, to 
refer them to various ages between the cretaceous and the pliocene, but more recent 
observers have been led to include all of these ophiolites in the upper eocene. This view 
was first advanced for those of the mainland of Tuscany by De Stefani, in 1878, and has 
since been maintained by Lotti, Taramelli, Issel, Mazzuoli and Capacci, among others. 
The horizon in the upper eocene to which these observers refer the serpentines in question, 
consists of argillaceous and marly shales alternating with beds of limestone and sandstone, 
and is below the argillaceous limestones with fucoids and nemertilites, but above the sand- 
stone known as macigno, which is found at the base of the eocene in Liguria. 
§ 90. As regards the origin of serpentines, Pellati remarks that the recent studies of 
Italian geologists have led to hypotheses which differ widely from those fornierly received, 
according to which serpentines were regarded “as plutonic or eruptive, having come to 
the surface after the manner of volcanic lavas, or at least, like certain massive trachytes, in 
a pasty state, or one of igneous semi-fluidity.” Gastaldi, he adds, “ from his studies of 
the ancient serpentines of the Alps, regarded them, however, as sedimentary rocks, modi- 
fied by subsequent hydrothermal actions operating at great depths in the earth.” He 
compared their formation to that of the accompanying gneisses, mica-schists, chlorite- 
schists, crystalline limestones, diorites, and even the granites, syenites and porphyries of 
the Alps, to all of which he ascribed an aqueous origin. 
§ 91. This hypothesis has not, however, been favorably received as an explanation of 
the origin of the so-called tertiary ophiolites of the Tuscan and Ligurian Apennines. Tara- 
melli, from his studies of the serpentines of the valley of the Trebbia, declared that neither 
the above mentioned view of their igneous eruptive origin, nor that maintained by Gas- 
taldi could be conciliated with the facts of the stratiform and lenticular arrangement of the, 
masses of serpentine, the want of evidences of alteration in the interstratified layers of. 
limestones and argillites, and the absence of ophiolitic dykes in these same rocks. He was 

