220 
FOKEiaN EQUIVALENTS. 
allow of free cominimication between Italy and France, and 
probably therefore with England. 
The land and freshwater mollusca of the Val d’Arno agree 
with the plants in their want of similarit}^ with living forms. 
Eleven species are recorded by Prof De Stefani, all being 
extinct, and none of them corresponding with British Pliocene 
fossils.* ]n fact half a dozen widely distributed living species, 
and one extinct snail {Helix suttonensis) are the sole links that 
connect the Pliocene land and freshwater mollusca of England 
with either the living or extinct species of Italy. It would seem 
that the route through the Riviera, so easily passed by the 
migrating mammals, was impracticable for freshwater mollusca, 
for the small streams are all at right angles to the path. For this 
group the western Alps would probably form a complete barrier. 
The occ urrence of the fresh water Liihoglyphus fuscus of the 
Danube fossil in England, and the absence of all the charac¬ 
teristic Pliocene freshwater shells of Italy, lends further coun¬ 
tenance to the suggestion that the fi*eshwater mollusca may have 
followed a dilferent line from that pursued b}^ the mammalia, and 
that they may have crossed the Alps at the low divides which 
separate some of the head-waters of the Rhine and Elbe from the 
Danube. Any new species of freshwater shells which may yet 
be discovered in our Pliocene beds ought perhaps to be found 
also in Austria rather than in the Val d’Arno, but at present 
the Upper Pliocene fauna of central Europe is imperfectly 
known. The Pliocene strata of the Vienna basin consist of 
Congeria-heds, with Lower Pliocene mammals, such as Mastodon, 
Deinotherip^m, Acerotherium, and Hipparion A somewhat 
similar mammalian fauna occurs at Epplesheim, in the Mainz 
basin, in sand and gravel with lignite ; but in both districts the 
later stages of the period seem to be unrepresented. 
Since these pages were in type, advance sheets have been 
received, thanks to Or. Lorie and M. Van den Broeck, of a new 
paper on some deep borings at Amsterdam.f One of these 
borings, that at Diemerbrug, descends to a depth of 1,096 feet 
below the sea-level, but it is doubtful whether any portion of 
this great thickness of newer Tertiary deposits is so old as the 
Diestian. Dr. Lorie was at one time inclined to refer the strata 
between 265 and 320 metres (867 to 1,047 feet) to the Diestian 
series; his list of mollusca obtained between these depths is 
therefore quoted :— 
Calyptraea sinensis. 
Chemnitzia densecostata. 
-elegantissima. 
-indistincta. 
Fusus scalariformis. 
Natica Alderi. 
Pleurotoma turricula. 
Eingicula ventricosa. 
Rissoa reticulata. 
Turritella terebra. 
Anomia ephippium, 
Cardita orbicularis. 
Cardium edule. 
-subturgidum. 
Corbuia contracta. 
* Molluschi Contmentali Pliocenici d’ltalia. Atti Soc. Tosc. Sci. Nat., 1876-84. 
f Lorie, Contribution a la Geologic des Pays-Bas. Part IV.—Les deux derniers 
Forages d’Amsterdam. Bull. Soc. Beige Geol., vol. iii., pp. 409-449. (1890.) 
