186 
CROMER FOREST-BED. 
The large number of mammals already known from the 
Forest-bed, seems clearly to point to a connection with the 
continent and to wide plains over which the animals could roam. 
We can hardly suppose that had Britain then been an island, it 
could have supported so large a fauna, including about 15 species 
of deer, three of elephant, and numerous other large forms. At 
present our acquaintance is principally with the aquatic 
mammals, or with those which inhabited the open plains, the 
Newer Pliocene upland and sylvan forms being still imperfectly 
known. A study of the lists of fossils shows, therefore, that we 
may expect to discover in the Cromer Forest-bed not merely a 
fauna and flora equal to that now living in this country, but one 
as varied in character as that of central Europe, with the addi¬ 
tion of numerous large mammals which, since the close of the 
Pliocene period, have been exterminated by the cold of the 
Glacial period or by human agency. 
The freshwater mollusca point even more decidedly than the 
mammals to continental conditions. There are only 48 species 
now living in the whole of Britain ; but we have already dis¬ 
covered 41 in the Forest-bed within a very limited area. Taking 
into account the absence in these lacustrine deposits of many 
of the species needing swiftly running water, it seems safe to 
conclude that only about two thirds of the species then inhabiting 
Britain have yet been discovered. This would make the molluscan 
fauna much larger than it is at present, but the occurrence of a 
considerable number of exotic forms in tlie Forest-bed shows that 
it may well have been so. 
In the last chapter attention was drawn to the very arctic 
character of the marine fauna of the Weybourn Crag ; a character 
which, as the late S. Y. Wood so ably showed with regard to 
the mollusca, became steadily more and more prominent during 
the whole of the Pliocene Period, from the Coralline Crag 
upwards, through the gradual dying out of the southern forms, 
and multiplication of the northern. But when we turn to the 
land and freshwater mollusca the result does not correspond ; 
for of the 59 species now determined from the Forest-bed, 
48 are at present living in Norfolk, 6 are extinct,* 2 are con¬ 
tinental forms living in the same latitudes as Norfolk {Hydro- 
hia Steiniif Sweden and near Berlin, and Valvata fluviatilis, 
Belgium and Germany); and the other 3 are all southern forms 
not now living in northern Europe {Hydrohia marginata, South 
of France, Lithoglyphus fuscus, Danube, and Gorhicula flumi- 
nalis, Nile). There is not a single species having an especially 
northern range. It may be objected that the Forest-bed fauna 
and that of the Weybourn Crag are not exactly contemporaneous, 
* Dr. Sandberger has described six other species as new. These have not 
been included, as they are evidently varieties of living forms. The figures given 
by Dr. Sandberger are not accurate, but good specimens of all the forms will be 
found in the Museum of Practical Geology. See Palceontographica, Band vii,, 
p. 83. (1880.) 
