11 
THE MEDITERRANEAN NATURALIST 
lithological characteristics as are exhibited by 
these pebbles. Their origin is, therefore, at 
present a mystery. 
Proceeding down the valley in a westerly direc- 
tion, four mounds of blue and yellow clay, (the 
marl beds of Spratt, and Adams), are to be seen 
resting conformably on the southern slope at 
an elevation of about 20 feet above the bottom of 
the valley; and in two instances patches of the 
black and yellow sands, that are invariably 
found to overlie the marl formation in other parts 
of the island, are also present. 
On the summits of these clay heaps there occur 
other portions of the Pleistocene bed ; but unlike 
those that have just been described, they are not 
in situ , but have been formed apparently by the 
degradation of beds that were originally situated 
higher up the slopes. 
The materials of which they are composed 
appear to differ but little from those of the other 
portions of the bed, save in the total absence of 
perfect shells, and in the comminuted condition in 
which the fossil bones are found. 
Such are the principal characteristics of the 
Pleistocene deposits that are found along the 
southern slope of the Dueira valley. 
If now, the road which winds up the hill-side 
towards Gebel-ta-Ben Giorgio be traversed, the 
observer will pass from the Giobigerina Limestone 
of the depressed district, across the line of fault 
marked by the Lower Limestone, to the Giobi- 
gerina above it. 
On the right hand side of the pathway that 
runs through this elevated region, and at a distance 
of about a quarter of a mile from the village of S. 
Giorgio another remmant of the bed is to be seen. 
Descending the hill again, and crossing to the 
northern slopes similar accumulations of even 
greater extent are to be met with. 
These portions of the beds, however, present 
many striking points of dissimilarity to those that 
we have just noted on the southern sides of the 
valley. 
Like the deposits on the opposite slopes they 
extend in an East and West direction, and they 
lie unconformably on the Giobigerina Limestone. 
They occupy a kind of platform on the hillside; 
and, towards the lower boundai y they break off 
and form escarpments of from 6 to 8 feet in 
height. 
The section may be thus divided. 
A. A greyish non-crystalline, slightly indurated 
limestone. Helices and other land shells occur 
in abundance; but no mammalian remains are 
present. 
B. Limestone of a similar character to A, inters- 
tratihed with irregular layers of stalagmite. 
These layers vary from | to £ of an inch in 
thickness. 
C. A layer of boulders and pebbles, all of which 
have apparently been derived from Beds IV. 
and V. Some of the boulders measure 18 
inches and 2 feet in length; and all of them are 
rounded and otherwise much waterworn. 
D. Loam intermixed with great quantities of 
smaller pebbles are found in this seam in great 
abundance. 
E. A yellowish grey loam, similar in every res- 
pect to that which occurs at the base of the 
other deposits. It also abounds with land- 
shells, but no mammalian remains appeared to 
be present. 
The distinct evidences of stratification that are 
apparent in the deposits on both sides of the valley, 
afford unequivocal proofs of their sequous origin; 
and this conclusion is still further borne out by 
the rounded and otherwise waterworn state of the 
pebbles that occur so plentifully in them. 
The finer detritus, the pebbles, the shells, and 
the mammalian remains have all, apparently, been 
collected from the surfaces of the surrounding 
country by the agency of freshets and inundations 
of a similar character. 
That no ordinary floods such as now occasionally 
occur in the winter time could have been engaged 
in the work of erosion and transportation is de 
monstrated not only by the contents of the beds 
themselves, but also by the nature of the gorges 
that have been cut in the strata in the immediate 
vicinity. Of these the Kaura gorge, a deep and 
rugged valley of erosion, is a striking example, 
the character of which points to the former exist 
ence of a much greater catchment basin than that 
which now exists, and to climatal conditions that 
must have been in direct variance to those that 
pow endure, 
