404 
The Mediterranean naturalist 
It would be irrelevant to liere consider these 
beds in detail ; I shall, therefore simply regard the 
formation as being broadly divisible into three 
sections, i.e. 
a. Deposits containing from 30 per cent, to 80 
per cent, of carbonate of lime; the residue being 
principally made up of alumina with a small quan- 
tity of silica. Dr. John Murray considers this 
portion of the bed to have been formed on a des- 
cending sea-floor in about 300 fathoms of water, 
and to have been within the influence of river- 
waters and their detrital products. 
b. Deposits containing from 80 to 90 per cent, 
of carbonate of lime.. Probably deposited in about 
1000 fathoms of water. 
c. Deposits containing 70 per cent, and less of 
carbonate of lime; and consisting for the most 
of the remains of comparatively shallow-water 
organisms. These were laid down on a rising sea- 
floor, and in about 300 fathoms. 
The Globigerina limestones may, therefore, be 
considered as being a series of deposits laid down 
during a gradual but constant change in the posi- 
tion of the sea-bottom, the deposits in division b. 
having been formed about the time when the ma- 
ximum depression was being attained, and at a 
considerable distance from any shore- line. 
In the lower parts of this intermediate division 
considerable quantities of siliceous concretions are 
found to occur in certain localities, of which the cliffs 
at Former Rih, the escarpments around the slopes 
of Uied Mars-el-forn, Uied Sakkaja, and Uied 
Hempisa, and the quarries of Tad-duai, Tal Gauchi 
and Inghieret furnish some of the most character- 
istic specimens. In none of the more impure 
varieties of limestone in either the upper or the 
lower di visions have any specimens been found. 
The concretions assume a variety of forms occur- 
ring sometimes as irregularly shaped masses of 
two or more feet in length, and from six to twelve 
inches in thickness, or as spheroidally shaped 
nodules having more or less symmetrically shaped 
outlines. In composition they also vary greatly, 
the larger masses being composed of flint (silexj, 
while the smaller nodular forms consists of chert, 
(phtanite,) which is an impure calcareous variety 
of flint. 
At Fomtner ilih and along the hill-slopes alrea- 
dy referred to, the differential degradation to 
which the nodular masses and their matrices have 
been subjected has resulted in the complete isola- 
tion of the former, ann they have thus been caused 
to project from the faces of the cliffs and escarp- 
ments as bold conical bosses. 
In none of the nodules are these exposed por- 
tions entire, as all of them have been more or less 
acted upon by the same meteoric agencies that 
have removed the limestone from around them. 
In many instances the disintegration has pro- 
ceeded by the peeling off of laminated scale-; while 
in others small shapeless masses have broken 
away and left the weathered surfaces irregularly 
prismatic in character. 
Viewed with the naked eye both the nodules 
and the larger masses are exceedingly homoge- 
neous; but when examined under a low magni- 
fying power, sections of foraminifera, small mol- 
luscs, and other organisms are to be seen embedded. 
In none of the specimens that I have examined 
have I observed any of the fish-scales to which 
Spratt alluded in his brochure ; but I cannot ven- 
ture to say that, therefore, such remains are either 
absent or of rare occurrence. 
In colour both the flint and the chert vary 
widely, graduating through all the intermediate 
shades of gray, fawn, bloe, and black. 
The interiors of the nodules are generally of a 
jet black colour, a fact which is probably due to 
the presence of carbonaceous matter, as much of it 
disappeared when subjected to the action of the 
blow-pipe tiame. This black interior often gradua- 
tes into a semi-translucent grey towards the outer 
edges, thus causing the concretions when cut 
transversely to present the appearance of being 
made up of a series of concentric layers of varying 
hues ; such specimens are not, however, so com- 
mon as are the uniformly black, grey, and fawn 
coloured varieties. 
The limestones surrounding the masses and the 
nodules is invariable changed into chert more or 
less pure in character. This cherty limestones is 
often of a colour similar to that of the enclosed 
nodule, »and unless carefully examined it is often 
difficult to say where the line of demarcation bet- 
ween the two lies, 
