[MATTHEW] STUDIES ON CAMBRIAN FAUNAS 193 



«arliei- sub-fauna before the introduction of the hiter. We have every 

 reason, therefore, to think that this sub-fuuna is homotaxically as recent 

 as that of the Andrarum limestone. 



Beside the species derived from the Acadian Middle Paraduxides sub- 

 fauna and those common to the European Upper Paradoxides beds, there 

 is a third element in this sub-fauna, with its fullest expression in the 

 Cambrian of the Hudson-Champlain valley, and in that of the slopes of 

 the Rocky Mountains, though present, also, in those of China ; this is the 

 genus Dorypyge, easily recognized by its markedly spiniferous pygidium. 

 Three species of this genus are found in the sub-fauna, two of which are 

 mere varieties of the western species, D. Wasatchensis (= (jothicus, and 

 D. quadriceps. The third is a species which had a row of spines along the 

 rachis of the pygidium, and which, in this respect, was like D. Marconi, 

 Whittield, of the Lake Champlain Cambrian, but had fewer segments in 

 the pygidium, and so, probably, a separate species. 



Eelation to the Olenellus Fauna. 



Through the above genus it would seem that a strong connection is 

 established with the Olenellus fauna of the Hudson-Champlain valley and 

 the Western States. This genus Dorypyge appears to be unknown in the 

 Lower Cambrian of Europe and Eastern Canada (Acadia). In both these 

 regions there is a continuous succession of sub-faunas in the Lower Cam- 

 brian, in which no trace of this genus has been found, but it makes its 

 appearance here in the upper part of the Lower Cambrian and in the 

 Western States, characterizes the Middle Cambrian (probably the lower 

 part), a fauna which contains it, therefore, cannot be regai'ded as Lower 

 Cambrian, unless an upper portion of that section of the Cambrian 

 system. The connection of Olenellus with this genus suggests that the 

 place of Olenellus is above Paradoxides, or in the upper sub-zones which 

 carry this genus. 



The non-occurrence of the two latter genera in the same beds, or at 

 least their rare occurrence together, may be due to the fact that one was an 

 inhabitant of shallow, warm, sandy shores ; and the other, colder, deeper 

 water, more freely laden with muddy sediment. Both in Scotland and in 

 the Rocky Mountain region, Olenellus is found in thin shaly partings at 

 the top of great thicknesses of sandstones or quartzites. 



If we depended solely on the lithology of the beds, we would say 

 that the place of the Hastings Cove fauna was between Protolenus and 

 Paradoxides, as the sandstones below are lithologically like those that 

 carry the former fauna (Protolenus. etc.), and the black shales above 

 certainly contain the latter (Paradoxides, etc.) But such a conclusion 

 would be quite at variance with the succession of faunas which have been 

 established in Scandinavia, Wales, and elsewhere in Eastern Canada, in 

 the Lower Cambrian beds. We are, therefore, compelled to assume that 

 the Hastings Cove fauna is as recent as the Upper Paradoxides beds. 



