APPENDIX. 13 



Similar opinions have also been ably advocated by Viscount d'Archiac, in his most recent publications 1 ; and 

 I feel convinced that, as we progress in our examination of the organic world, we will perceive the 

 absolute necessity of seeking some other explanation for the successive replacements, than that attributable 

 to partial convulsions, upheaval of mountains, or limited unconformity of stratification. 



M. d'Orbigny's researches have been principally directed to the study of the Mesozoic and Tertiary 

 formations, as seen in France, which has led him to divide that extensive period into twenty-one distinct 

 epochs ; each (in his opinion) characterised by a complete or almost entire change in the animal creation ; 

 while during the much more extended Palaeozoic period he only sees reason for admitting four. Convinced 

 that such is the unvaried law of nature, and that matters will so remain, he proposes to designate each of 

 these successive creations by a distinct and defined number ; thus, were we alluding to the epoch of the 

 Gault, we might simply say, nineteenth age. The whole Silurian period would be No. 1 ; the Devonian, 

 No. 2 ; and so on until we reach the Jurassic and Cretaceous periods, wherein the succession of successive 

 changes would have been so rapid, that in the first he admits ten, and in the second seven, each according 

 to his system, having as much value, or being as entirely independent, as the whole Silurian, Devonian, or 

 Carboniferous periods, Nos. 1, 2, and 3 ! 



That such a system was, to say the least, hazardous, becomes each day the more apparent : has not M. 

 Barrande already shown that the Silurian age in Bohemia, as well as in many other countries, are 

 susceptible of being separated into three distinct natural divisions ; each (so far as his researches extend) 

 possessing a distinct animal creation, which he designates as faunes pritnordiale, seconde, and troisieme, and 

 with equal, if not greater, claims to count as 1, 2 and 3, as M. d'Orbigny's Jurassic age has to Nos. 7, 8, 

 9, 10, 11, 12, 13, 14, 15, and 16? 



It would, therefore, follow that if M. d'Orbigny's newly proposed practice were admitted, viz., that of 

 designating a distinct creation or epoch by the simple mention of the number he has imposed, M. 

 Barrande's numeration would essentially differ from that adopted by the author of the ' Palaeontologie Fran- 

 caise.' Such a system, leading at once to the most pernicious results, cannot be too strongly opposed at its 

 very birth, as all mistaken views, if allowed to take root, are infinitely more difficult to remove after they have 

 become familiarised by habit. Besides which, the real value of several of these divisions are, in many cases, 

 more than problematical, 2 and in my opinion, as well as in that of other palaeontologists, it is very probable 

 that it may soon be found absolutely necessary to restrict considerably the number of the distinct creations 

 introduced into the Mesozoic and Tertiary periods. 



We will now revert to some of the species in the order in which they have been published : 



Page 8, Lingula. 



Besides Ling. Beanii, Phil., and L. ovalis, Sow., several doubtful specimens have been forwarded for 

 examination, but not perfect enough to warrant an accurate identification. 



1 'Histoire des Progres de la Geologie,' vol. iv, pp. 2 and 3, and vol. v, 'Introduction,' pi. 6 to 12, 

 1853; also, 'Bulletin de la Soc. Geol. de France,' vol. x, p. 423, 1853. I would strongly urge the 

 importance of every geologist and palaeontologist becoming acquainted with the observations published 

 by this celebrated author. 



2 In a very interesting memoir, published by Mr. L. Saemann, in the ' Bull. Soc. Geol. de France,' vol. 

 xi, second series, p. 261, 1854, an attempt has been made to place in comparison and parallelism the dif- 

 ferent British subdivisions of our lias, inferior oolite, and great oolite, with some of their equivalents in 

 France and Germany. The table is good and useful, as it settles some of the much-vexed questions relating 

 to the comparative age of many of the continental beds. 



