MACKIE — ON THE BOTTOM-ROCKS. 



153 



shrimps, grubs, and other small creatures that lived iu 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 under 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, and a 

 specimen, three yards in length, is now under examination iu Jermyn 

 Street. 



THE COMMON FOSSILS OF THE BRITISH ROCKS. 



By S. J. Mackie, F.G.S., F.S.A., etc. 



{Continued from 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 be 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 



