on the Taconic System, 



115 



and those of the Potsdam sandstone, in the occurrence of six 

 species of Dikellocephalus and one of Menocephalus ; while the 

 occurrence of many others is in agreement or not incompatible 

 with the fauna of the Potsdam and Calciferous sandstones. The 

 comparative values of the trilobitic faunae of this group and of 

 the primordial zone of Europe, as established by Barrande, is 

 better shown in a tabular form which T here append. 



The Crustacean fauna of the 'primordial zone of Europe. 



Paradoxides, 

 Olenus, 

 Peltura, 

 Conocephalus, 

 Ellipsocephalus,* 

 Hydrocephalus, - 

 Sao, - - - 

 Arionellus, 

 Agnostus, - 

 Amphion, - 



These genera are all limited to the primordial 

 fauna^ and none of the other European 

 genera of trilobites are known in this fauna. 



Of the first and second fauna. 

 Placed with doubt in the first fauna, and is 

 well developed in the second fauna. 



The Crustacean fauna of the Quebec Group. 



Conocephalus, 

 Arionellus, - 

 Agnostus, - 



Dikellocephalus, - 



Menocephalus 



Bathyurus, 



Asaphus, 



lUsenus, 



Amphion, - 



Ceraurus = Cheirurus, 



Genera of the primordial zone. 



A genus passing from the first to the second 

 fauna. 



Genera of the Potsdam period. 



Quebec group. 



Of the second fauna. 



Of the second and third fauna. 



Of the second fauna ; and doubtfully of the 



first fauna in Sweden. 

 Of the second and third Silurian faunae, and 



of the Devonian fauna. 



We have therefore in the Quebec Group, two established gen- 

 era of the primordial zone ; one, Agnostus, which passes from the 

 primordial to the second fauna ; one, Amphion^ cited as doubtful 

 in the first fauna in Sweden, and known to be in the second ; 

 and three, — Asaphus, Hloenus and Cheirurus, which begin their 

 existence in the second fauna. Of these, Asaphus begins and 

 ends in the second; lllcenus begins with the second and continues 

 to the third ; while Ceraurus = Cheirurus begins in the second, 

 extends through the third Silurian, and appears in the Devonian 

 fauna. 



Not Elliptocephalus of Emmons. 



