212 Dr A. Philippi om the Recent and Fossil Mollusca of the 
formerly the various circumstances, the localities, the nature 
of the sub-marine land, &e., were more favourable for the 
development and growth of certain species, but were also less 
favourable for the development of a very few species; and 
that, speaking generally, these various circumstances were at 
that time similar to those of the present day. 
IV. What is the proportion of the living and extinct species 
at the individual localities 2? Have all the latter a like age? 
Can subdivisions be established in the Tertiary formation of 
Southern Italy ; and if so, what are they ? 
In general, the fossils are chiefly abundant in clay, in marl, 
and in shell sand; but it is of no importance for the object of 
the present memoir, to describe petrographically the individual 
localities, more especially as the same petrifactions occur in 
the clay and in the shell sand, and even in the compact lime- 
stone, as can be well seen near Palermo. Ina similar man- 
ner, it may be remarked, the same recent species occur, at 
the present day, on sandy shores, as well as on muddy coasts, 
&e. The geognostical phenomena, so far as Sicily is con- 
cerned, have been most fully described by my late friend 
Frederick Hoffmann, in his “ Geognostische Beobachtungen, 
gesammelt auf einer Reise durch Italien und Sicilien.” 
I propose soon to give a detailed description of the tertiary 
formation of Calabria ; the distribution of that formation is 
very distinctly delineated in the map which Von Tschikalschoff 
has copied with perfect exactness from original materials 
furnished by me. I would refer my readers to that gentle- 
man’s ‘ Coup d’oeil sur la constitution geologique des provinces 
meridionales du royaume de Naples.” 
If we place together all the individual localities of Sicily, 
&e., and arrange them according to the proportion which 
the extinct species bear to the living, beginning with the lo- 
calities which present the largest number of extinct species, 
and ending with those which afford the smallest, we shall 
evidently exhibit them in the order of their relative ages ; 
for the first must, of course, be regarded as the oldest, and 
the last as the newest. 
