THE DISTRIBUTION OF ANIMALS AND PLANTS. 491 
Secondary rocks included a vast assortment of fossils whose 
general appearance was more like recent forms. This great 
division of time was terminated by the deposition of our upper 
chalk beds. Then came the third or last great division of time 
in which recent forms made their appearance. With the ex- 
ception of several lowly-organised animalculae and the one 
species of shell-fish he had mentioned, none of the secondary 
life-forms were now in existence. But w 7 hen we came to the 
Tertiary period the case was different. Shell-fish then made 
their appearance, and w r ere now found fossilized, which un- 
doubtedly belonged to existing species. Taking the several 
stages of this great division of time, uaturalists found that in 
proportion as they neared the human epoch the per-centage 
of living species was largely increased. One of the last of the 
stages of this epoch was that when our own Bramerton crag 
was deposited, and any of them would have seen from 
the shells in that neighbourhood how like they were 
to those they might pick up on the sea-beach. To esta- 
blish a more scientific analysis of the same shells it was 
found that out of more than a hundred species all were 
still in existence with the exception of two or three. And 
yet this Norwich crag, as it was termed, must have been • 
formed scores of thousands of years before man made his 
appearance. All the thick beds of sand, gravel, and clay of 
Great Britain had been formed along the bottom of the sea 
w 7 hich had covered nearly the whole of the British islands 
since then. It was when we compared the different fossils in 
the recent strata that we were struck with their near affinity 
to living forms elsewhere. The oldest warm-blooded animals 
termed Marsupials made their appearance in the early part of 
the Secondary Period. For ages they swarmed over what w 7 as 
then Europe and other portions of the globe. At length they 
became successively extinct, and the only members of the class 
now in existence were living in America and Australia. Their 
widely severed geographical areas indicated the time this group 
had been in existence, for the Australian continent had be- 
come isolated in the mean time. Then, again, one of the 
earliest mammals in the Tertiary epoch was nearly allied to 
the modern tapir. These, like the preceding, had had more 
or less of a cosmopolitan distribution. They were now limited 
to tw T o species living in South America, and one in the Malay 
Archipelago. Their present isolation was accepted as a proof 
of a former land connection, for the most orthodox stickler 
for special creations would never contend for a creation 
of the same species in two different parts of the w 7 orld. 
The geographical distribution of some animals told a most 
