80 REPORT—1857. 
flexures and hy an extensive fault, yet the same series exists, only the relative extent 
of the different mineralogical formations is different ; the red and the light-grey lime- 
stones being there very little developed, while the variegated schists are much more 
so, and have a black limestone interstratified with them, corresponding in position to 
a marly limestone, which is found in other places, also interspersed among these 
schists, and which is remarkable for the abundance of fucoids that it contains. This 
Jurassic limestone with fucoids is not to be confounded with the other succeeding 
Cretaceous and Eocene limestones, of which we shall speak hereafter, although the 
species of these fucoids are in general very difficult to distinguish. Nor yet is this 
black limestone, intercalated among the mottled schists of La Spezia (and which is cer- 
tainly of the jurassic period), to be confounded with another fossiliferous black lime- 
stone of the same locality, which belongs to the cretaceous system, and to which also we 
shall presently advert. It was just the confounding of these two limestones that gave 
rise to so many discussions and to so many false interpretations respecting the struc- 
ture of the western promontory of the Gulf of Spezia. Now the ammonites described 
by Sowerby and many others, which occur at La Spezia in the lower beds of the 
variegated schists, and in the black limestone therewith interstratified, are the same 
as those which are to be found in a like position in the light grey limestone in the 
Pisan Mountains. They are of species belonging to the Lias, and many of them have 
been recently recognized at Hierlatz by Hauer. These same species of ammonites 
of La Spezia, of the Monti Pisani, and of Hierlatz, have been also recently found in 
a sparry limestone at Campiglia. There the variegated schists are wanting, and the 
limestone occupies the fissures existing in the red ammonitic limestone. Finally, 
another recent discovery has been made to complete the series; in the upper part of 
the variegated schists of La Spezia, there have been found in great abundance, casts 
of ammonites of species totally different from those already indicated, and perfectly 
recognizable as belonging to the “‘ Oxford clay.” 
The black fossiliferous limestone which is in superposition to the Jurassic schists of 
La Spezia, is represented in the Apuan Alps, and in the Monte Pisano, by a lime- 
stone of like character, but rarely containing fossils. Itis remarkable that in the same 
locality of La Spezia, we find it, at the distance of a few paces, decidedly metamor- 
phosed into a most beautiful Portovenere or Portoro marble, or into white dolomite, 
and extremely rich in fossils exposed by the erosive action of the sea. In the Apuan 
Alps this forms the second peripheric band, and constitutes the lofty summits of 
the Pania, Pizzo d’Uccello, Pisanino, &c. The fossils which it includes prove it to 
be cretaceous, but with regard to its synchronism with the rocks of other localities, 
nothing more can be said than that it corresponds to the most ancient of the cretaceous 
periods, which elsewhere has been called “‘ Neocoinian.”” ‘The remainder of the cre- 
taceous rocks of the Tuscan Apennine and of the metalliferous chain, is chiefly com- 
posed of two mineralogical formations, a flaggy limestone, more or less arenaceous, 
denominated ‘ Pietra forte,” which constitutes the material with which the city of 
Florence is paved, and argillaceous schists frequently altered into hanife and jaspers, 
in contact with the ophiolitic volcanic masses. These schists, locally denominated 
«* Galistri,”’ also contain, more or less abundantly interspersed, a white, cream, or 
lead-coloured limestone, denominated “ Alberese;” and finally, there appear in it 
beds of micaceous sandstone, “ Macigno,”’ which, at last prevailing over the schist 
formation, constitutes the chief bulk of our Apennines. In many places the Alberese 
limestone is partially replaced by some inconsiderable beds of nummulitic limestone, 
- often containing nummulites of many species and well preserved, together with a 
great quantity of the other fossils which usually accompany them ; sometimes, instead, 
with the nummulites small or fragmentary, in which case it takes the name of “ Cal- 
care screxiato.” When this member of the stratigraphic series exists, we have the 
means of distinguishing the portion of it, which, being lower in position than the num- 
mulitic band, belongs to the cretaceous system, from the upper part, which, together 
with the nummulitic formation itself, ought rather to be considered as Eocene Tertiary, 
But where there does not exist any nummulitic bed, as frequently happens, it is not 
possible to draw any line of separation. It is to be observed, by the way, that the 
mineralogical character of the “ Pietra forte’ seems to resemble closely that of the 
Macigno sandstone; but not only are they in reality distinct, and their stratigraphical 
position very distinct, but moreover it was in the Pietra forte that Micheli found the 
Vall y yaa ae 
—— oe 
