42 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [NOV. 19, 



However we may seek to account for the absence of a varied fauna 

 in the Cambrian strata, the fact is rendered the more remarkable 

 by the occasional abundance of the phosphates, sulphates, and 

 lluates, as well as of graphite, in the Silurian basement-rocks, which 

 immediately followed the Cambrian by tranquil deposition. 



III. Abundance of Life above the Cambrian. — Not a few natural- 

 ists are inclined to believe that in the mollascan form of life, from 

 the earliest times, instead of an ascendant movement in their order 

 of development, a decadence even has affected them ; and that these 

 organisms of distant date do not yield in specialization to the like 

 forms of today. A tendency to concur in such opinions may well arise 

 from a consideration of the following facts, which show at the same 

 time how abrupt and great must have been the change from life in the 

 subjacent strata, to life in the Silurian ; from a state, that is, of great 

 comparative sterility, to one singularly prolific. 



a. Tracks of Crustaceans. — First, the occurrence in the Potsdam 

 Sandstone (the oldest Silurian) about the mouth of the Ottawa, that 

 noble river, and about Lake Louis into which it flows, of footprints 

 and tracks of several species of large Crustaceans. They have been 

 faithfully described by Sir W. E. Logan and Professor Owen, be- 

 sides having been most generously illustrated by the former. These 

 appearances carry the existence of complex forms of life very far 

 down. 



b. Pliosphatic Coprolites ivith Lingular. — Secondly, while James 

 Hall, the great palaeontologist of America, found in the Dclthyris 

 Shaly Limestone (Upper Silurian) coprolite-like, phosphatic nodules, 

 full of crushed Linyulce, the Geological Commission of Canada met 

 with facts more remarkable still. They discovered that a large 

 breadth of country on the Ottawa Eiver, from Lake Allumettes to, 

 at least, Grenville, a distance of 80 miles in the south-east direction, 

 is more or less sown with coprolites in calciferous sandstone. This 

 rock, at the Falls of the Allumettes, is a conglomerate, and rests 

 directly on Laurentian gneiss. 



These coprolites are sometimes 2| inches long by i an inch broad, 

 and are filled with a large species of Liwjida ; in one case a frag- 

 ment of this shell was found lying crosswise in the nodule. Besides 

 the Lingular, a few Pleurotomariai or Holop&ai are met with in these 

 reniform masses. 



The Grenville coprolites are smaller and more compact than those 

 of Lake Allumettes. They give off an animal odour when heated, 

 and principally consist of phosphate of lime, as do those of the 

 Township of Hawksbury, close by. These latter are yellowish brown, 

 and smell like burnt horn when heated. Dr. Lyon Playfair proved 

 that similar bodies from the Bala Limestone, in North Wales, were 

 foreign bodies of animal origin*. All phosjmatic nodules may not 

 be coprolites ; but these from the Ottawa have every appearance of 

 being so. 



The coprolites of Lake Allumettes, &c, seem to be the excretions of 



* Quart. Journ. Greol. Soc. vol. vii. p. 2G7. 



