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________________________ "ON FOSSIL MAMMALS," FULLERIAN PROFESSOR OF PHYSIOLOGY ROYAL INSTITUTION ETC. "Summary of the Succession in Time
and Geographical Distribution HAVING thus recounted the chief steps which have been made in the restoration of the extinct quadrupeds of Australia, I conclude the physiological deductions from this class of organic phenomena , and the selection of topics, which seemed to me to be best adapted for the present Fullerian course. In the discourse of to-day, as in the preceding one on South American extinct mammals, you could not fail to he struck with the forcible and cumulative evidence which they supplied in proof of the law that with extinct as with existing mammalia, particular forms were assigned to particular provinces, and that the same forms were restricted to the same provinces at a former geological period as they are at the present day. That period, however, was the more recent tertiary one. In carrying back the retrospective comparison of existing and extinct mammals to those of the eocene and oolitic strata, in relation to their local distribution, we obtain indications of extensive changes in the relative position of sea and land during those epochs, through the degree of incongruity between the generic forms of the mammalia which then existed in Europe, and any that actually exist on the great natural continent of which Europe now forms part. It would seem, indeed, that the further we penetrate into time for the recovery of extinct mammalia, the further we must go into space to find their * Printed by Request. existing analogues. To match the eocene palaeotheres and lophiodons we must bring tapirs from Sumatra or South America; and we must travel to the antipodes for myrmecobians, the nearest living analogue to the amphitheres and spalacotheres of our oolitic strata. On the problem of the extinction of species I have little to say and of the more mysterious subject of their coming into being, nothing profitable or to the purpose, at present. As a cause of extinction in times anterior to man, it is most reasonable to assign the chief weight to those gradual changes in the conditions affecting a due supply of sustenance to animals in a state of nature which must have accompanied the slow alternations of land and sea brought about in the aeons of geological time. Yet this reasoning is applicable only to land animals; for it is scarcely conceivable that such operations can have affected seafishes. |
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