FAUNAS NOT UNIVERSAL 287 



now exist. Herein we find a justification for those 

 hypothetical shore-lines which so many geologists now 

 seem driven to assume. 



We must not, in our zeal for extending our knowledge 

 of zones and their distribution, be misled into the unreal 

 assumption that the faunas of these zones were world- 

 wide in their extension ; that is by no means the case. 

 Kegional provinces, distinguished by species peculiar to 

 them, would seem to have existed as far back as the 

 geological record extends. Possibly the number of cosmo- 

 politan species was, on the whole, greater in the early 

 stages of the earth's history than it is now, but such a 

 phenomenon as a universal fauna or flora has not yet 

 been brought to light. This, however, is all pure gain, 

 for if the zonal fossils enable us to link the several pro- 

 vinces together, the regional species, on the other hand, 

 provide us with a means of discriminating between 

 them ; while the one points out the lie of an ocean 

 shore, the other indicates the position of some dividing 

 barrier. 



We have seen what causes may have contributed to 

 bring about a rapid and widespread distribution of 

 species, but we must not omit to repeat that these by 

 themselves would not provide us with species useful for 

 zonal purposes ; for this, organisms must exist charac- 

 terised by the special facility they display for specific 

 transmutation. Such, in opposition to those sluggish 

 forms Lingula and Nautilus, were the Graptolites and 

 Ammonites, which are almost startling in the rapidity of 

 their change. Speaking in the language of metaphor, we 

 might remark, especially with regard to the Ammonites, 

 that they impress us as alert and intelligent beings, seek- 

 ing by rapid Protean changes to escape an impending fate, 

 postponing their doom successfully throughout the whole 

 of Mesozoic time, and then succumbing to the inevitable, 



