hunter's published paper on fossils. 291 



naturally supposed to consist chiefly of those of one class or order in 

 each place, one principle acting in such places." The principle here 

 alluded to is the grand result of the extensive zoological researches 

 which have since established it, under the term of the ' Geographical 

 distribution of animals.' Hunter's first glimpse of it seems to have 

 begot as great a difficulty in its expression as that of the resemblance of 

 the phases of embryonic life to the series of inferior forms of animal 

 species, which he was the first to enunciate [p. 203]. But, in both cases, 

 he has recourse to explanations of his meaning, and tries to deliver himself 

 of the same idea in other forms of words ; thus, after the first enunciation 

 of a supposed localization of particular classes or orders of animals, " ac- 

 cording to one principle," Hunter next proceeds to say : — 



" In considering animals respecting their situation upon the globe, 

 there are many which are peculiar to particular climates ; others that 

 are less confined ; and others again which, probably, move over the whole 

 extent of the sea, as the shark, porpoise- and whale-tribes ; while many 

 shell-fish must be confined to one spot." 



And here, by the way, it is interesting to find that the migrations of 

 the marine animals to which Hunter alludes, as ' probable ' in the species 

 recited, are precisely those regarding which zoologists of the present day 

 still entertain some difference of opinion ; but all seem now agreed that 

 certain Cetacea of the southern hemisphere differ specifically from those 

 of the northern seas. As to the application of the law of Geographical 

 distribution of animals to fossil remains, Hunter's philosophical suppo- 

 sition has been abundantly confirmed, by the marsupial character, e. g., 

 of the fossil mammalia from the caves and tertiary deposits in Australia 

 — the land of kangaroos ; and by the gigantic sloths, armadillos and 

 anteaters, whose remains occur " under circumstances so similar" in 

 South Am erica, to which tract of dry land true anteaters (Myrmecojihagce), 

 armadillos, and sloths are now, and seem ever to have been, confined. 



Hunter, in the memoir from which I quote, next proceeds to touch 

 upon the nature of the evidences by which fossil remains might eluci- 

 date the changes of temperature to which different parts of the earth 

 may have been subject at different epochs ; and he points out more di- 

 stinctly, and with more detail, the evidence which extraneous fossils 

 afford, respecting the alternations of exposure and submersion, or of dry 

 land and sea, to which different parts of the earth have been subject at 

 different epochs. 



" Prom a succession of such shif tings of the situation of the sea, we 

 may," he writes, " have a stratum of marine extraneous fossils, one of 

 earth, mixed probably with vegetables and bones of land animals, a 

 stratum of terrestrial extraneous fossils, then one of marine productions ; 



tj2 



