Dr. J. J. Bigsby on the ' Thesaurm Siluricus.* 297 



group probably becomes fused, and assumes their horizontal position, 

 mineral character, and many of their organic contents. 



The fauna of the Quebec group, consisting of 327 species at Point 

 Levi (Quebec) and in Western Newfoundland, is peculiar, and, of 

 course, is only found there, with the exception of thirteen species 

 found elsewhere in Calciferous sandstone, and eight in Chazy Lime- 

 stone. They are one-sixteenth of the whole, and are as follows : — 



Calciferous Sandstone : — Lingula ManteUi, L. acuminata, L, 

 Irene, Camerella calcifera, Helicotoma gorgonia, H. uniangulata, 

 H. perstriata, Pleurotomaria calcifera, P. postumia, Holopcea dilu- 

 culal, Ecculiomphalus Canadensis, Murchisonia Anna, Piloceras 

 Canadense (Billings). 



Chazy Limestone : — Ecculiomphalus Atlanticus, Maclurea Atlan- 

 tica, Stromatopora compacta (running into B + BL), Climacograptus 

 antennarius, Ptilodictya fenestrata 1, Leperditia amygdalina, Came- 

 rella varians, Cheirurus prolificus (Billings). 



This group contains, besides the thirteen species just enumerated, 

 1 74 * aUied to those of the Calciferous Sandstone of Central North 

 America, or more or less westward of Montreal. It is this which 

 connects it closely with the sandstone. However, 140 remain 

 typical. 



The fossils of Chazy Limestone met with in the Quebec group 

 only belong to a few of the basement beds of the former, because 

 these almost immediately, upwards, change into a compact mass 

 of crushed Crinoids, Cephalopoda, Gasteropoda, &c. (143 species) 

 — all quite new, and alien from the life below. 



The Calciferous Sandstone, always truly primordial, has in the 

 Canadas and the United States of America 375 species, overspread- 

 ing vast areas. They may be separated into three sets : — 



\. Thirteen enter the Quebec group. 



2. One hundred and seventy-four are the allies of that group. 



3. One hundred and eighty-eight are foreign to it, and for the 

 most part typical. 



Like its two sister groups, the Calciferous Sandstone is shown, 

 in the middle line of Table D, to display a remarkable tendency to 

 abound in complex and powerful existences, and to paucity in the 

 simple species, individuals nevertheless being prodigiously numerous. 

 Trilobites are here very few. 



Potsdam Sandstone is rich in Trilobites, Brachiopoda, and Fucoids, 

 but in every other form is very poor ; and yet it possesses a Cystid. 



In the Primordial group, therefore, we find numerous representa- 

 tives of nearly every marine Invertebrate ; and we have a startling 

 example of the sudden development in very early times of the highest 

 types of moUuscan life, — Nautili, Lituites, Trilobites, Protichnites, 

 &c. dwelling, even then, in well-adjusted communities. 



Most of these facts are taken from the * Thesaurus ;' but this in- 

 teresting portion of the * Thesaurus ' itself is the gift of Barrande, 



* These numbers are for the present only approximate, and may be altered. 



