[MATTHEW] NOTES ON CAMBRIAN FAUNAS, No. 12 49 
The Protolenus fauna was so named from the presence in it of 
two species of the genus Protolenus occurring at different horizons in 
this zone; of these P. elegans, W. D. Matthew, is by far the most 
abundant, and also most widely distributed vertically, and with other 
genera of trilobites, Ostracods, &c., give character to the fauna. 
The exact reference of the several species to their special layers, is 
due to the careful work of Messrs. W. D. Matthew and Gilbert van 
Ingen, students in the School of Mines of Columbia University, when 
a study of the Cambrian measures of this fauna was undertaken. 
One condition of preservation of the organic remains of this zone was, 
that many of the fossils were preserved in or attached to nodules of 
phosphate of lime in the shaly layers, and thus had their exact form 
preserved; and were not flattened, nor distorted, asare many of the fossils 
found in the mud beds of the Cambrian system. The Swedes who 
have studied the occurrence of phosphate nodules in the Cambrian 
strata of their own country have offered the opinion that this compound 
has been derived from the decay of organic forms which have this 
substance in their tests, and that the deposit of this mineral only 
occurs where the water is comparatively clear, and the sea shallow. 
The nodules have been found only at the eastern end of the St. John 
basin of Cambrian rocks; tho’ the typical forms of trilobites of this 
zone, have been met with at both ends of the basin and in the next 
basin to the north; but the fossils of the eastern end of the St. John 
basin, were chiefly depended on for the determination of the species. 
In extending the study of the Cambrian rocks of the Maritime 
provinces of Canada to Nova Scotia, it was found that in the island 
of Cape Breton the volcanic rocks (felsites, &c.) which underlie the 
stratified rocks in that island contained, at Dougald brook, shaly 
layers holding Brachiopods and Ostracods of Cambrian type, and of 
genera, most of which could be duplicated in other areas of Cambrian 
rocks, it was therefore thought that these rocks should be referred to 
the Cambrian system. There was however, on this brook, one pe- 
culiar genus of Brachiopods which has not been found elsewhere in 
the Cambrian rocks. Hence tho’ there was no proof, by fossils, that 
the great mass of volcanic rocks at the base of the Cambrian (the Cold- 
brook) were of Cambrian age it seemed proper to include them in 
the Cambrian System on account of the conditions in Cape Breton. 
The Paradoxides Fauna 
The profusion of animal forms which are found in the lower 
gray shales of the St. John group are divided off into zones by the 
localization of certain Cambrian trilobites which serve as horizon 
markers. The following may be taken as typical: 
