176 NATURAL SCIENCE. Sept.. 



France, so that southern land animals could cross freely. The same 

 land barrier, however, isolated the North Sea, so that it was only open 

 towards the north, and not only was the sea therefore colder than the 

 air, but only northern species could enter this enclosed area, and any 

 southern forms happening to die out could not be replaced. For this 

 reason it is probable that the temperature of our Newer Pliocene sea 

 may not have been quite so low as the marine fossils alone would 

 appear to indicate. 



Though the Cromer Forest-bed is not visible in the immediate 

 neighbourhood of Ipswich, yet as it is intended so to arrange the 

 excursions as to give an opportunity of examining all the Pliocene 

 •deposits, a short description of this stage may be useful (3). 



The Cromer Forest-bed consists of a series of land, freshwater, 

 and estuarine deposits formed in the delta of a large river, which 

 seems to have been a continuation of the Rhine across the shallow 

 bed of the North Sea. Though thin, these deposits are of great 

 interest, owing to the prolific fauna and flora which they contain, 

 aad to the evidence which they yield as to climatic conditions im- 

 mediately previous to the Glacial Epoch. The plants of the Forest- 

 bed, and also to a large extent the invertebrate fauna, show a close 

 approximation to the present inhabitants of our Eastern Counties ; 

 for though the occurrence of such species as the spruce fir, the water- 

 chestnut, and the extinct Pavadoxocaypus carinatus would give a peculiar 

 •character to the flora in the eyes of a botanist, yet any ordinary 

 observer would only notice the forests of oak, Scotch pine, beech, 

 birch, elm, hazel, hornb am, and cornel. The lakes were full of 

 yellow water-lily, water-crowfoot, and various existing species of 

 pondweeds, their shores were occupied by thickets of alder and 

 willow, of osmunda, or dense growth of reeds and sedges. Amid 

 these the few and rare extinct plants might easily be overlooked. 



If, however, while wandering through these Pliocene woods or 

 along the shores of the Pliocene broads we were to meet with any 

 of the larger mammals, this illusion would be entirely swept away. 

 Nearly all the larger species are now entirely extinct or are extinct in 

 Europe. Among the most abundant were three species of elephant, 

 two of rhinoceros, a hippopotamus, two horses, and various peculiar 

 deer. The carnivora included bears, hyaenas, the machserodus, and 

 the glutton. Among the rodents was a gigantic beaver. A few of 

 these large mammals survived down to Pleistocene times, and some 

 are still living, but most of them appear to have been exterminated 

 •during the first glaciation. 



The stages immediately succeeding the Forest-bed are still, not- 

 withstanding all our efforts, most imperfectly understood. Marine 

 sands overlying the Forest-bed near Cromer contain in one place 

 arctic shells, in another a bed of oysters, which cannot stand intense 

 cold. Between these marine sands and the earliest Boulder Clay 

 occur patches of laminated clay and loam, often very suggestive of 



