1867.] 



^ Thesaurus Siluricus.' 



379 



These few facts have been selected from many, to show the strong ten- 

 dency to locahzation inherent in the Silurian fauna, 



Primordial Stage. 



The * Thesaurus' amply manifests the great extent of this stage, and the 

 high significance of its teachings ; but we shall here only speak of a few 

 leading facts relating to Canada, extracted from the ' Thesaurus ' itself. 



While waiting for the results of field-work now in progress, Mr. Billings 

 has treated this subject with his usual great ability in the first volume of 

 the work entitled * The Palaeozoic Fossils of Canada.' 



The Primordial stage of Barrande (Taconic of Emmons) is truly Silu- 

 rian, and forms the base of that epoch. 



In the valley of the St. Lawrence it may average 8600 feet in thickness. 



Resting horizontally in America on the inclined Laurentian rocks, the 

 lower break is complete in every respect ; while the upper break is very 

 nearly so, although purely organic. 



It divides naturally into Lower and Ujiper Primordial, — Potsdam sand- 

 stone constituting the former, and calciferous sandstone, with the enig- 

 matical Quebec group, the latter, with a few layers of chazy limestone 

 superadded. 



The whole flora and fauna of the Primordial stage, American and Eu- 

 ropean, amount to 919 species, while those of the St. Lawrence Valley 

 alone are 560. The western, therefore, seems to be the richer of the two 

 hemispheres ; and this comes out still more distinctly in stating the fact 

 that the Primordial genera at present known in America are 134, and those 

 of all Europe 83. 



Table D (below) has been constructed from the 'Thesaurus.' It exhibits 

 numerically the zoological contents and the zoological relations of the 

 several parts of the Primordial stage ; and we see that the differences are 

 great. 



Table D. — The American Flora and Fauna of the Primordial Stage 

 (principally Canadian). 







morphozoa. | 



nnelida. 



.etero-Pterop. | 



ryozoa. | 



oophyta. | 



rinoidea. | 



ystidea. | 



steriada. | 



_c3 



C3 



>^ 



g 



o 

 o 



asteropoda . | 



racbiopoda. | 



epbalopoda. | 



1 



ntomostraca. | 



isces. j 



otal. 





Ph 



<1 



<l 







N 



O 



Q 





p 









Q 



H 





Ph 



B 



r Quebec Group 



Upper j 





4 



21 



19 



44 



2 









5 





57 



42 



34 



96 



3 





327 

























[ Calciferous Sandst.... 



6 



5 



3 



5 





1 









1 





39 



6 



19 



6 



2 



? 



93 



LoAVER Potsdam Sandstone . . . 



16? 



2 



4 



2 



1 







1 









3 



31 



74 



6 



140 



























Total 



1 



22 



11 



28 



26 



45 



3 





1 





6 





99 



79 



53 



176 



11 





560 



Great interest attaches to every part of this stage, but especially to the 



