36 LOWER AND UPPER SILURIAN FORMATIONS: 



portion of time represented by the Lower Silurian and Sub- 

 Silurian rocks. We cannot believe that it presents us examples 

 of all the genera of animals which existed in that age ; and 

 there is some force in the remark, that we generally see in it 

 the products of deep seas only, and cannot know what other 

 seas of shallow character may have produced. But, as far as 

 positive evidence goes, we cannot but be sensible that the 

 palaeontology of the period indicates creation at a low stage 

 purely marine destitute of fish, exhibiting families, generally 

 speaking, low in their respective lines of gradation. 1 And 

 yet this was a state of things which lasted throughout a vast 

 space of time, for the great thickness of the Lower Silurian 

 strata can only be interpreted as the record of many ages. It 

 is important to remark the co-existence of fucoids with the 

 very oldest of yet discovered fossil animals. As animal life 

 must depend primarily upon vegetation for support, we might 

 have been sure beforehand that plants preceded, or were con- 

 temporaneous with, the animal creation. Such, however, did 

 not at one time appear as the order of fossils, and when, ulti- 

 mately, fucoids were discovered in the earliest fossiliferous 

 formations, it was felt that palaeontology had come into a har- 

 mony with nature which was not to be dispensed with. 2 



UPPER SILUEIAN. 



THE Upper Silurian formation, presenting in the ascending 

 order in England the Wenlock shale, the Wenlock limestone, 

 the Lower Ludlow rocks, the Aymestry Limestone, and the 

 Upper Ludlow rocks, may be described as giving us a continua- 

 tion of the fauna of the preceding formation, with some 

 changes of species, and some additions. The brachiopod, the 



1 See Proofs and Illustrations, No. 6. 



2 In the Lower Silurians of Sweden, not only are there distinct im- 

 pressions of such plants, but Professor Forchhammer speaks of courses 

 of true coal, composed, as he thinks, of sea- weed, and gives an opinion 

 that the alum-slate of that country owes its combustible character to the 

 carbon, sulphur, and potash derived from marine vegetation. Murchi- 

 soris Geology of Russia in Europe. 



Mr. Daniel Sharpe has brought under the notice of the Geological 

 Society the very remarkable fact of a coal basin from 1000 to 1500 feet 

 thick, existing in Portugal, below rocks characterised by their fossils as 

 Lower Silurian. This coal bed contains plants generically, if not spe- 

 cifically, identical with the ferns of the carboniferous series ; therefore 

 inferring dry land and a land vegetation, in some parts of the earth, at 

 this early period. 



