142 THE MIDDLE PAST. 



and this in a genetic line backwards through the prior 

 epochs of the chalk and oolite. In some of its minor 

 features the oolite may find an analogue in existing nature, 

 but in its entirety it stands alone a great life-epoch, whose 

 forms are not to be confounded either with what has gone 

 before, or with what has yet to follow. 



The Cretaceous or Chalk period, to which we next turn, 

 brings to a close the long and exuberant line of niesozoic 

 life. Great changes in the relative distribution of sea and 

 land in the northern hemisphere have been gradually 

 brought about ; much of the oolitic sea-bed has become 

 dry land ; and the areas of deposit have assumed a less 

 southerly aspect. Stretching more in an easterly and 

 westerly direction, they present less variety of climate, and, 

 opening up to the north, they become recipients of currents 

 which tend to deteriorate the more genial conditions of the 

 oolitic era. Greensands, clays, clay-marls, and chalk of vary- 

 ing consistence form the prevailing sediments, which, being 

 eminently marine, are replete with the remains of oceanic life. 

 Little of the terrestrial surface of the period is indicated by 

 the fossil flora or fauna, and much of the marine area in 

 Asia and in America has been but imperfectly explored. 

 Notwithstanding this imperfection of the record, we find 

 enough to corroborate the ever -onward progression of 

 vitality, and to show that oolitic forms, though by no 

 means rare, are gradually being replaced by others peculiar 

 to the chalk and greensand. 



The Flora, though scantily preserved, has still somewhat 

 of an oolitic aspect, looking more like the remnants of that 

 age than the peculiar products of a newer epoch. Sea-weeds 

 (confervitcs and chondrites) resembling the living confervas 

 and Irish-moss, ferns (lonchopteris\ lily-like leaves (dra- 

 cwna), cycads (zamiostrobus and dathraria), and coni- 



