12 APPENDIX. 



assertions only shew the limited experience of those who make them : nor is it sufficient to state that such 

 and such a form is a derivative, except we can demonstrate the source whence the form has been derived, 

 and explain, both by words and figure, wherein the natural connexion or sequence lies. But let it not be 

 imagined, from what has just been stated, that it is my wish or intention to deny that some of the so-termed 

 species enumerated in this monograph are in reality more than simple variations, referable to one single type. 

 In many instances I have expressed doubts as to their distinct specific claims ; and if I did not combine 

 certain forms, it was because the material then at my disposal was not sufficient to warrant such a conclusion. 



There is also another point no less worthy of investigation, viz., what relative value or importance 

 should we attach to the minor local divisions in the strata made use of in geological works ? Professor Forbes 

 states l that " the marine faunas of the oolitic epoch indicate at least three great and widely spread 

 assemblages of types, each exhibiting a general and easily recognisable facies. These aspects may be 

 termed respectively the liassic, the Bathonian, and the Oxfordian ; the two latter terms being used for want 

 of better, and being adopted in a wide and general sense, and not in the restricted meaning in which they 

 are used by M. A. d'Orbigny. The horizon of change of facies at the boundary between each is a horizon, 

 to a considerable extent, of change of species. I believe that every year's research will make it more 

 evident that the perishing of species is simply the result of the influence of physical changes in specific 

 areas, and depends upon no law of inherent limitation of power to extent in time. If so, we should expect 

 to find indications of the cause of the greater changes in the oolitic and marine fauna in the shape of strata 

 bearing evidence of a wide-spread change of physical conditions within the great oolitic area. An extensive 

 change of species within a marine area in all likelihood is dependent on an extensive conversion of that 

 area into terrestrial surface." 



The questions relating to the existence of species in time, as well as of the cause of their sudden 

 disappearance, and replacement by others, are among the most important inquiries within the domain of 

 palaeontology, and have of late years particularly occupied the thoughts of several of our most distinguished 

 foreign and British naturalists. 



M. Barrande informs us, 2 that his views on this subject differ materially from those recently circulated 

 by several illustrious men in their most recently published elementary works. According to which 

 doctrines, the different animal creations characterising the vertical sequence of formations (Terrains) have 

 been suddenly destroyed by violent convulsions of the earth's surface (cataclysmes), annihilating at once all 

 the then existing animal creation : so that each of these universal revolutions (according to their theory) 

 would explain, in a very plausible manner, the complete renewal at different periods of all the animal forms 

 on the surface of the globe. M. Barrande admits that this renewal in many cases cannot be contested ; 

 but asserts that the change is not in all instances due to convulsions of the earth's surface, of which he 

 quotes several remarkable examples among the Palaeozoic deposits. It seems to him more rational to admit 

 that the phenomena of the development of the series of beings in time, taken as a whole, is subjected to a 

 special law of nature, independent of that which governs the physical revolutions of the surface of our 

 planet j that since we see all these faunas disappear in succession, one after the other, from the entire 

 surface of the globe, at defined and limited periods, never to be reproduced under the same aspect, one is 

 tempted to believe that the same creative cause which has restricted in so abrupt a manner the existence of 

 individuals, has likewise imparted only a determined quantity of vital force to all the families of animals, 

 and, consequently, to each of the creations destined to occupy in succession the surface of our globe. 



1 ' Quarterly Journal of the Geol. Soc.,' vol. x, No. 38, 1854. Professor Forbes is referring to Professor 

 Morris's 'Researches in Lincolnshire,' published in vol. ix, p. 317, 1853, of the same journal. See also 

 Davidson, 'Bull. Soc. Geol., France,' second series, t. xi, p. 171, Jan. 16, 1854. 



2 'Bulletin de la Societe Geol. de France,' vol. x, p. 415, May, 1853; and ' Systeme Silurien de 

 la Russie,' vol. i. See also Barrande, 'Bull. Soc. Geol. France,' vol. xi, second series, p. 311, 1844. 



