132 .1. //. Clark— Recent Crmoid Faunas, 



The recents crinoids of the Australian coasts are evidently 

 senescent : they unmistakably indicate very great age. So 

 complete, in fact, is this senescence that almost every species 

 is affected. The crinoids of Australia came from the north- 

 Man!, from the great East Indian archipelago ; but here con- 

 tinual changes in the distribution of the land and sea have con- 

 stantly rejuvenated the fauna so that none of its component 

 species has been permitted to drift into the peaceful old age 

 so obvious in almost all the species along the Australian shores. 



The fossil crinoids of Europe (belonging to genera still exist- 

 ing) appear to be senescent ; but they are no more so, if as 

 much, as are the recent crinoids of Australia. Judging from 

 the evidence offered by the recent forms alone, the European 

 crinoids reached the European seas by passage from what is 

 now the Bay of Bengal north of what is now India. It was 

 probably before this that the same genera spread southward 

 from the parent central East Indian region to Australia. 



The crinoids of southeastern Africa represent a compara- 

 tively young fauna; they must have reached their present 

 habitat by passage southwestward from Ceylon along a land 

 bridge since submerged ; but few of them have as yet entered 

 the Arabian Sea. 



The West Indian fauna is younger again than that of the 

 southeastern shores of Africa, from which it was derived. It 

 must have reached the West Indies by following a land which 

 extended from Madagascar to the Antilles, north of what is 

 now southern Africa. 



The fauna of southern Japan is very young, apparently 

 younger than that of the West Indies. 



The central sea connecting the Bay of Bengal with cen- 

 tral Europe had an arm stretching northward across Bussia. 

 Certain adaptable genera, becoming acclimated, followed this 

 arm northward and gave rise to the present arctic fauna. 

 More recently one of these arctic genera has spread southward 

 over the north Atlantic. 



At a considerably later date a connection was formed whereby 

 the East Indian crinoids, becoming slowly acclimated, reached 

 the antarctic regions. There was also a connection between 

 the antarctic regions and southern South America, whereby 

 these forms secured a foothold on the western coast of that 

 continent, spreading rapidly northward to the Aleutian Islands 

 (dipping downward into deep water when passing under the 

 tropics), and thence southward along the eastern coast of Japan, 

 as far a,s Tokyo Bay. 



This antarctic fauna is apparently the youngest of all the 

 recent faunas, and the evidence of youth increases as we go 

 northward along the west American coast. 



U. S. National Museum, Washington, D. C. 



