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gnthUslti&t, but it was far otherwise, when they reflected for a moment that 

 the processes of nature were slow and onward, and that the last few thousand 

 years had failed to effect any very great or important changes on the earth's 

 Surface, that the ancestors of some of the same species of coral polypes now 

 living in tropical seas had formed reefs that wore probably seventy thousand 

 years old, and if we remembered that this long period related only to existing 

 species, what must we think of the duration of those ages that had preceded 

 modern times?— that long vista of the past during which eighteen miles of 

 sedimentary rock had been slowly and steadily accumulating? and, be it noted, 

 it was at the very dawn of this far, far distant age when the creatures before 

 them sported their little day of existence in the Silurian seas. 



It was interesting, therefore, in a natural history point of view to inquire 

 in what the past differed from the present. Let them look first at those bsau- 

 tiful sea lilies, the Crinoids from the Wenlock limestone, see how nicely the 

 pelvic plates were jointed together like mosaic, and how finely the arms 

 branched off from the cup to form a net for catching prey, see how finely the 

 stem was jointed, consisting of hundreds of plates buUt upon each other, some 

 of these stems beijig rooted to submarine bodies, while others were tapering 

 and free ; examples of both conditions were on the table, so abundant wera 

 the remains of Crinoids in the Silurian and Carboniferous rocks, that many 

 thick beds of limestone were almost entirely* composed of their broken up 

 skeletons. We had two or three species of existing Crinoids in the seas of 

 the Antilles, but they were entirely distinct from those that lived in the 

 Silurian and other subsequent ages, although the general plan of their con- 

 struction and many details of their organisation resembled their old ancestors. 

 These Crinoids therefore ought to be carefully examined, for there were some 

 choice specimens before them. 



The next group of Radiates was the starfishes, of which many specimens 

 were on the table from the Ludlow rocks at Leintwardine. It was long 

 thought that the Crinoids were the only representatives of the Echinodermata 

 in the Silurian seas, but the discovery of these fossQs in rocks of the same 

 age in England and America had taught us to pause in our generalisations, 

 and examine nature more attentively. On one of the slabs from the Wenlock 

 limestone, there was a pretty specimen of Lepidaster, with its columns and 

 plates around the margin of the arms. From the Lower Ludlow rocks there 

 were various specimens of Pakcocoma and Protaster in different stages of 

 growth, interesting to all zoologists, as showing how faithfully nature had 

 adhered to the type of organisation so characteristic of the Asteriadw, and 

 proving that the present was connected with the past by a series of links which 

 united them in natural relation. Some fossil star fishes of the Lias beds so 

 closely resemble existing species of that family, that it required the most 

 careful diagnosis, to detect the differences by which they were separated. 



Passing on to the next group of fossils before us, the oldest forms of the 

 articulate animals, we see a magnificent series of TrUobites, most of which 



