J. VV. GREGORY — RELATIONS OF ECHINOID FAUNAS. 



101 



The following paper was then read : 



THE RELATIONS OF THE AMERICAN AND EUROPEAN ECHINOID FAUNAS. 

 i;V J. W. GREGORY, P. G. S., F. Z. S., OF THE BRITISH MUSEUM OP NATURAL HISTORY. 



Contents. 



Introduction page 10] 



The Carboniferous Faunas i<^ 



Permian-Jurassic Faunas 103 



The Cretaei - Faunas L03 



Eocene ; 1 rn I 1 Higoeene Faunas 104 



The Miocene Faunas 105 



The Pliocene Faunas 107 



Summary of Conclusions 108 



Introduction. 



Probably every paleontologist who lives on the western border of the great 

 galearctic province occasionally chafes against the limitation which the Atlantic 

 places upon our knowledge of the origin or derivation of successive fossil faunas. 

 In many case,- researches on the paleontology of central and eastern Europe have 

 given the desired information as to the origin of a British or western European fauna ; 

 hut in other cases groups of genera and species appeal- suddenly in a certain zone 

 and as suddenly disappear. The probabilities in such cases are in favor of the mi- 



Errata. 



Page 101, line 13 from bottom : for "aquatic " 

 " 103, " 6 " " " "karstein" 



read agnostic. 



' 105, " 12 

 " 107, " 27 



" 107, " 18 



top, 

 bottom, 



" "twinned 



U {{ 



Asterostoma, n. sp.," 

 " " Asterostoma " 



Jcarsteni. 

 tumid. 



Archseopreuster abrup- 



tus, Greg. 

 Archseopreuster. 



ence in the mid- Atlantic to explain tiie ouiicuiTies oi pai euzouiu gica i uiauiumiun m 

 the old world : but, on the other hand, a school composed mainly of zoologists have 

 adopted a more aquatic attitude by accepting the theory of the permanence of 



oceans and continents, which leaves these difficulties unexplained. Certain 

 physical arguments have been adduced in support of^his view, hut they do not 

 seem of any great value, and the whole question seems to turn on zoological, and 

 especially on paleontological distribution. 11' the Atlantic has been permanently a 

 deep ocean basin uo such littoral tropical Torn is could have entered Europe from the 

 Wesi excepl during peri 01 Is when the arctic area enjoyed a temperate climate, and 



a theory which postulates a scries of such warm periods would he unsatisfactory 

 even if there were no1 evidence in some cases againsl the " northwest passage." 



The question is one of some importance to workers in mosl departments of paleon- 

 tology. The phylogenisl w ho accepts the theory of the permanence of oceans and 

 continents is likely to train the branches of his phylogenetic tree along very differ- 

 enl lines from those thai would be preferred by one who admitted the possibility 



