Phosphatic beds, supposed to have had a coprolitic origin, are found in the Lower Silurian rocks of Canada.
In the Lower Silurian formation at Plattsburg and Chazy, in Clinton county, are two beautiful grey or grey and pink marbles, one of which is a favourite among domestic marbles for mantels, table tops and other interior decorations.
So far, the two workers had been in agreement; but in his presidential address to the Geological Society of London in 1842 Murchison stated his opinion that the Cambrian contained no fossils that differed from those of the Lower Silurian.
Hicks to prove that the rocks below the undoubted lower Silurian of Murchison did indeed possess a characteristic fauna, and their work was confirmed by researches going on in other countries.
The order was more abundantly represented in Palaeozoic times by the Heliolitidae from the Upper and Lower Silurian and the Devonian, and by the Thecidae from the Wenlock limestone.
