216 DISTRIBUTION OF THE MOLLUSCA IN TIME. 



DISTRIBUTION OF THE MOLLUSCA IN TIME. 



The brevity and excellence of the remarks of Dr. Paul Fischer 

 upon the distribution in time of fossil mollusca, is my sufficient 

 apology for transferring them almost bodily to these pages, 

 distinguishing them throughout by quotation-marks : they con- 

 stitute a most valuable portion of his excellent " Manuel de 

 Conchjdiologie." 



" Fossils, considered at first," says Fischer, "as lusus naturse 

 or as the remains of animals like those which now people our 

 seas and continents, commenced to be differentiated from living 

 forms to-^ards the close of the last century. Buffon sustained 

 this opinion stremiously : ' The knowledge of all the petrifac- 

 tions, of which we no longer find living analogues, requires 

 lengthened study, and the thoughtful comparison of all the 

 species of petrifactions which have been found so far in the 

 bowels of the earth, and this science is not yet far advanced ; 

 nevertheless we are certain that there are several species such as 

 the Ammonites, the Orthoceratites,the Belemnites,etc.,to which 

 no existing species can be referred. * * * Their petrifaction is 

 the great means by which nature has preserved forever the 

 record of perishable beings ; it is in fact by these that we recog- 

 nize the most ancient productions and that we have an idea of 

 these species now annihilated^ the existence of which has pre- 

 ceded that of all living and growing objects; they are the sole 

 monuments of the earlier ages of the world ; their form is an 

 authentic inscription^ which it is easy to read in comparing them 

 ■with similar organized bodies. * * * It is above all among shells 

 and fishes, the first inhabitants of the globe, that we can count 

 a very large number of species which no longer subsist ; I will 

 not undertake their enumeration here, which, although lengthy, 

 would be still incomplete ; such a work upon ancient nature 

 would alone require more time than yet remains to vnj life, and 

 I can only recommend it to posterity.' 



" This passage indicates clearly that Buff'on already considered 

 fossils as a means of establishing the chronology of stratified 

 rocks. In the inquiry which he indicated, Cuvier and A. Brong- 

 niart in France, and W. Smith in England, almost simultaneously 

 engaged. The two former, in 1808, remarked that the fossils 

 distributed in each bed generall}^ remain the same throughout 

 its extent, but difler in passing from one bed to another. This 

 character serves to distinguish the beds, and to recognize their 

 recurrence at distant localities. ' This is a mark of recognition,' 

 the}^ say, 'which so far has never failed us.' 



"A. Brongniart is still more explicit in 1822 : ' In order to 

 characterize the strata, one must not only designate the species 

 found in them, but designate them all, determine them verv 



