Reviews — Barrande's Silurian Cephalopoda. 489 



We should take care to mention here that M. Barrande divides his 

 geographical distribution of the Cephalopoda into three parts : — 

 A. Grand Central Zone of Europe, which includes Bohemia, 

 France, Spain, Portugal, and Sardinia. B. Grand Northern Zone, 

 subdivided into I. Europe, Great Britain, Norway, Sweden, Eussia, 

 Thuringia, Franconia, Saxony, Germany, and Holland. II. North 

 America, Newfoundland, Acadia, Canada, New Brunswick, New 

 York, Wisconsin and Illinois, Missouri and Tennessee. C. Divers 

 Countries, consisting of the Himalayas and Tasmania. 



After investigating the principal phenomena presented by the 

 successive evolution of the Cephalopoda in the vertical series of the 

 Silurian deposits, M. Barrande has endeavoured to ascertain how far 

 that chronological evolution accorded with the zoological develop- 

 ment of the group, and he then proceeds to draw a parallel between 

 the two. 



This concordance, M. Barrande observes, would be at once evident 

 if the most simple forms appeared first, and the most complex last, 

 in the series of Silurian rocks. The author maintains, however, 

 that such is not the case. 



Thus the most simple forms, the Ascoceratides, do not appear until 

 the close of the second fauna in Canada, and at the commencement 

 of the third fauna in Bohemia ; whilst forms the most complex, such 

 as Nautilus and Trochoeeras, appear at the beginning of the second 

 fauna in America, so that it would seem there was an interval of 

 nearly the length of the entire series of deposits forming the 

 second fauna of Barrande, before the appearance of the simple 

 forms, during the whole of which period the more complex forms 

 had existed. 



These facts the author considers are sufficient to show that there is 

 an irreconcilable discordance between the chronologic and zoologic 

 evolutions. 



M. Barrande considers that the total absence of Cephalopods in the 

 Primordial Silurian strata does not permit us to suppose that the 

 earlier types were developed during the existence of a hypothetical 

 series of Anteprimordial faunas of which not a trace remains. 



In replying to M. Barrande upon this point it is needful to be most 

 cautious, for this reason, that he has gone so carefully into this grand 

 question that it is hardly possible to find a flaw in the conclusiveness 

 of his reasoning. We would, however, venture to suggest a few 

 points deserving his attention. 



And first as regards the regions explored. M. Barrande has 

 probably achieved more, single-handed, in the country of Bohemia, 

 for the exploration and investigation of its fossil fauna, than has 

 been done by the united labours of many men for any other 

 country in the world. The result speaks most eloquently from 

 the pages of M. Barrande's great work. In the Cephalopoda which 

 we are now considering, we find the number of genera and species 

 enumerated from Bohemia alone to exceed that of any other region 

 in the world hitherto explored. 



