N THE GEELONG NATURALIST. 
has been repeatedly proved by experiment. Those shells found in 
the tropieal seas are far more brilliant in colour than those found 
in temperate climes. A 
The duration of life in the mollusca is little known. Some are 
supposed to live but one year or season, others two, as the land 
snail. Again, others exist many years; and probably the ridges on 
the surface of many genera are the terminations of their yearly 
growth. Having thus given an outline of shells and inhabitants, we 
will glance back at their fossil representatives. The remains of these 
are found in all formations, from the Laurentian upwards, and 
although some of the orders exists to the present day, all the species 
are extinct, with the exception of a few who make their appearance 
in the latter portion of the tertiary period. To form some idea of 
the life of a specie, let us glance at the Mississippi Riverin America, 
This river, itis estimated, has taken 100,000 years to form its delta, 
and drive the sea back 500 miles, and yet, at the commencement of 
its course, by sinking a shaft, you get the same shells that are living 
in the sea at the present time; this shows there has been no change 
of species in that time. ‘Then again, on our own coast at Barwon 
Heads, Spring Creek, and Eagle Rock at Airey's Inlet, the same 
thing occurs; the shells we find on the beach we find on the tops of 
the hills. The base of Eagle Rock is volcanic rock& of probably 
cretaceous or early eocene age, all above this is marine eocene 
limestone, crowded with fossils. In my notes on the rock, made at 
the time where—first, some volcano of cretaceous or early eocene 
age poured its stream of lava over the land, these rocks became in 
time the sea shore, for on them we find the fossil limpets just as 
we find the limpets of the present day on the rocks; then the land 
gradually snk, till at last it was 40 fathoms deep, then the coral 
limestone was formed; but a change took place, and the land slowly 
rose again, then became once more the sea shore. 
HALL & Sons, PRiNTERS, GEELONG. 
