180 
CROilER FOREST-BED. 
occurs between these divisions, for at fii^st sight the species living 
during the two periods seem to have been quite di:ffierent. They 
also point to somewhat different climatic conditions. The Forest- 
bed has sometimes, for this reason, been separated from the rest 
of the Pliocene strata, and has been called Older Pleistocene. It, 
however, yields a very different fauna from that of the true 
Pleistocene deposits with which it is thus correlated. 
When examined more closely, and. with the advantage of the 
greater amount of positive evidence now available, the Norwich 
Crag and the Forest-bed are found to be intimately allied. 
They are so closely connected, that they can only be separated 
as slightly different horizons in the same period. The real 
break, if a line must be drawn, is above the Forest-bed not below 
it. 
Let us examine first the marine mollusca—always taken as 
the test to decide questions of this sort. These, unfortunately, 
are very poorly represented in the Forest-bed. There are only 
19 species yet known; of which several may be derived from 
the Weybourn Crag. Thej^ are all common We 3 ’'bourn Crag 
shells, and include several extinct forms, such as Melampus pyra- 
midalis, Tellina ohliqna, and Nuciila Cohboldice. As lar as 
they go, they tend to show that there has been no change in the 
molluscan fauna. There are several arctic species among them ; 
indicating that the temperature of the sea was also little 
altered. 
The other marine fossils of the Forest-bed are the Cetacea and 
the Seals. These also point to boreal conditions; but so little 
is yet known of the species belonging to the Weybourn Crag 
and to the Chillesford Clay, that no comparison is possible. 
Mr. Newton has now determined nine species from the Forest- 
bed. Of these one—a walrus {Tridiechus Huxleyi) —is a 
characteristic Crag form ; the others are still living. The next 
Cetacean fauna below the Forest-bed lies at the base of the Red 
Crag, in the Nodule Bed. 
Among the few marine fish yet known from the Forest-bed 
the characteristic Upper Pliocene Platax Woodwardi is the 
most abundant. It is more plentiful on this horizon than any¬ 
where else. The tunny (Thynnus thynnus), recently discovered 
in the Forest-bed, is a fish belonging to warmer seas than ours. 
Probably the single vertebra found belonged to a stray indi¬ 
vidual, like those that visit our coast at snort intervals, and stray 
even as far north as Shetland. This completes the marine fauna 
of the Forest-bed. It is evident that a close connexion exists 
between this horizon and the Weybourn Crag; but until we 
have considerably larger lists of fossils, it will be impossible to 
say whether the deposits are nearly continuous, or whether there 
is a slight gap between. 
Turning next to the inhabitants of the land, and of the lakes 
and rivers, we find plenty of material for an analysis of the 
Forest-bed fauna and flora, but little for comparison with the 
older strata. Freshwater strata are unknown in the rest of our 
