192 DR. THOMAS STERRY HUNT ON THE 
zone pass into quartzose mica-schists, often including almond-shaped masses or segrega- 
tions of quartz and feldspar, sometimes with large plates of mica. It would appear from 
the descriptions of Lotti, that these serpentines of Corsica belong to the upper horizon 
defined by Gastaldi, above the recent gneisses, and in what we have designated as the 
fourth group of Alpine crystalline rocks. (§ 69) The underlying protogine is, according to 
Lotti, a talcose gneiss. 
§ 73. The resemblance of these rocks to those associated with similar serpentines on 
the neighboring island of Elba is declared by Lotti to be very close. There also the ser- 
pentinic horizon is underlaid by gneisses and mica-schists, as in Corsica. He concludes 
with Gastaldi that the great crystalline zone of the Alps is connected through the Mari- 
time and Ligurian Alps with the similar rocks of Corsica and Elba. Resting upon the 
ophiolitie strata in Elba are found, according to Lotti, paleozoic carbonaceous slates con- 
taining Orthoceras, Cardiola, Actinocrinus, and probably also graptolites. Lotti, however, while 
he asserts the great antiquity of all of the serpentines of Corsica, and part of those of Elba, 
maintains the existence in the latter island of other serpentines which, like those of Tus- 
cany, he refers to the eocene period. 
A similar question is raised with regard to the granites of the two islands. Thus 
Pareto, who regarded’as ancient, or at any rate pre-triassic, the granites of Corsica, admit- 
ted for the granites of Elba, Monte Cristo and Giglio a post-eocene age, a view which is 
also sustained by Lotti, while de Stefani, on the other hand, assigns the Elban granites to 
pre-triassic time. I can scarcely doubt that all of these granites, as well as the ophiolites 
both of the various islands and the mainland, will be found, as maintained by Gastaldi, of 
pre-paleozoic age. 
§ 74. If we turn to the island of Sardinia we find a series of pre-Cambrian crystalline 
schists, said to consist, in their upper portions, of argillites, sometimes talcose, sandstones, 
crystalline limestones and dolomites. These, which are referred by Bornemann to the 
Huronian or pietre-verdi zone of the Alps, are overlaid, as was first shown by de la Mar- 
mora, by a series of uncrystalline limestones, shales and sandstones, containing an abun- 
dant lower paleozoic fauna. * Of this, the Upper Cambrian (Ordovician) + forms were long 
since described by Meneghini. The subsequent studies of Bornemann, in 1880, showed at 
the base of the series a zone marked by Paradoxides, Conocephalites, Archeocyathus, etc., which 
have also been examined by Meneghini, and establish the existence of a Lower Cambrian 

* Bornemann, sur les formations stratifiées anciennes de la Sardaigne. C. Rendus du Congrès Géol. Inter. 
de Bologne, pp. 221-232. 
+ The term Ordovician, sometimes contracted to Ordovian, was proposed by Lapworth in 1879, (Geological 
Magazine, vi., p. 13,) to designate the group of paleozoic rocks found in Wales between the base of the Lower 
Llandovery and the base of the Lower Arenig. These, corresponding essentially to the Upper Cambrian or Bala 
group of Sedgwick—the second fauna of Barrande—were, as is well-known, by a mistake in stratigraphy, joined by 
Murchison to his Silurian system, under the name of Lower Silurian, and have also since been called Siluro-Can- 
brian and Cambro-Silurian. By making of this debated ground a separate region, between the true Silurian above 
and the great Cambrian series below, (the Middle and Lower Cambrian of Sedgwick) Lapworth has sought to get 
rid of this oonfusion in nomenclature, and to restrain the attempts of some to extend the name of Silurian down- 
wards even to the base of the Cambrian itself. This designation is convenient in American geology from the fact 
that it includes the group of strata between the base of the Silurian (Medina) sandstone and the base of the Chazy 
limestone; the latter, together with the Trenton, Utica and Loraine divisions, being equivalent to the Ordovician. 
The name was given in allusion to the Ordovices, an ancient British tribe inhabiting North Wales. 

