MACKIE — ON TIIIC UdTTOM-ROCKS. 
153 
shrimps, grubs, and otfior small creatures that lived in the shallows, 
or there sought a fitting place for the deposition of their spawn among 
the seaweeds of the period. 
One other specimen more, of vegetable-like matter, I shall just 
notice as falling luider observation that day. The forms of this 
substance have a spongy appearance, are of a deep red ferruginous 
colour, extend laterally in the rock several yards, and descend 
vertically into the matrix about a foot to a foot and a half Mr. 
Salter's attention has been called to this curious concretion, aud a 
specimen, three yards in length, is now under examination in Jermyn 
Street. 
THE COMMON FOSSILS OF THE BRITISH ROCKS. 
By S. J. Mackie, F.G.S., F.S.A., etc. 
{Continued fnmi Vol. I. page 289.) 
Chap. 3. The Remnants of the First Life-World, and the Bottom-rocks. 
In one of my last papers on the " Bottom-rocks" I appended a 
coloured map to a portion of the first dry-land of our mother-earth, a 
portion of the first division of the land from those waters " which 
covered the globe," a fraction of one of those primeval cracks or ridges 
which then remotely shadowed out our present continents and oceans ; 
and in the little green patches I gave all the traces known of the first 
beaches and sands which spread around those low and barren tracts in 
the great region of North America which I selected for an illustration. 
To this map I hope soon to add, as supplements, others of South 
America and of Europe. Africa must he left yet a long while ere one 
dare make the like attempt. To these maps, from time to time, I shall 
add colour after colour to show the successive deposition of those 
great rock-formations in which the animals and plants of the succes- 
sive life-creations of our planet have been entombed ; and I hope 
VOL. II. M 
