582 ZOOLOGICAL DISTINCTIONS OF SYSTEMS AND FORMATIONS. 



Is there one species of the Crinoidea figured in this work, known in the carbonife- 

 rous strata ? 



Has the Serpuloides longissimum, or have those singular bodies the Graptolites, or in 

 short any zoophytes of the Silurian System been detected in the well-examined car- 

 boniferous rocks ? 



And in regard to the corals, which are so abundant that they absolutely form large 

 reefs, is not Mr. Lonsdale, who has assiduously compared multitudes of specimens from 

 both systems, of opinion, that there is not more than one species common to the two 

 epochs ? 



If, therefore, it should prove after all, that a few species of conchifers (an order of 

 beings capable, perhaps, more than any other of enduring vicissitude), continued in 

 existence, from the formation of the Silurian Rocks to the accumulation of the carboni- 

 ferous limestone, how can their presence break down the individuality and separation 

 of systems, established upon such a vast preponderance of direct zoological evidence 

 in the other natural classes ? Even should a few other mollusca in the two systems 

 be considered identical, there is no doubt, that by far the greater number of them which 

 truly belong to rocks rising from beneath the Old Red Sandstone, are distinct from those 

 which inhabit the strata above that system. 



Such evidences are therefore, as before mentioned, nothing more than additional 

 supports of the important truth which geology has already established ; that each great 

 period of change, during which the surface of the planet was essentially modified, was 

 also marked by the successive production and obliteration of certain races. 



Let it not, however, be imagined that I wish to inculcate the doctrine, of every an- 

 cient formation having been tenanted by creatures absolutely peculiar to it. The large 

 natural groups of strata only, or, so to speak, systems, can be thus distinguished. We 

 have, indeed, ascertained to a great extent the distribution of organic life in the epochs 

 anterior to our own, and we now know, that with each great increment of newly depo- 

 sited matter, new animals appeared, and that while some vanished with the lapse of 

 time, others unsuited to sudden changes were destroyed. 



Among the secondary causes by which such results have been aided, the volcano 

 and earthquake have assuredly been most prominent. We believe, therefore, that 

 inasmuch as the outbursts of volcanic matter, in the region under review, have been nu- 

 merous and often repeated, they must have materially operated in the destruction of 

 animal life ; but as we have shown that all the lines of eruption were limited, so we infer 

 that no general destruction can have taken place ; and hence it is, that this territory, 

 when examined carefully and in all its parts, presents us with so many examples of a 

 perfect " sequence" in the succession of the strata and the progressive development of 

 their zoological contents. 



Thus certain species, whether endowed with powers to resist vicissitude or living in 

 those parts where few active agents of destruction were at work, continued to live 



