12 5 A. R. C. SELWYN ON THE 
Roxton and Farnham townships, they are certainly unconformably overlaid by the black 
slates and limestones of the Trenton group, and it seems quite probable that they are the 
northward extension of the Georgia, Vermont, Paradoxides slates. To the north-east, the 
largest exposure of these “Sillery” rocks commences in a point between Ste. Marie, on 
the Chaudiere, and Ste. Claire, on the Etchemin, where they appear to pass downwards 
without apparent break into the metamorphic group of the central axis, and to be uncon- 
formably overlaid to the north-west by Levis conglomerates and black graptolite slates. 
This area is described (page 257 of the Geology of Canada, 1863), but it has never been 
thoroughly investigated, and it seems that two distinct sets of rocks have been included 
in it. The lower is probably on the same horizon as the upper part of the metamorphic 
group, and the newer, also largely composed of red and green mottled slates and sand- 
stones, is closely connected with the Cambrian red and green slates, in which, at Point 
Levis and north-eastward, a small obolella has been found, the same fossil being sometimes 
associated in dark green or black argillitis, with species of Levis graptolites. 
As regards the order of succession of the strata composing what I have designated the 
fossiliferous belt, I have no doubt whatever it has been reversed, or, in other words, that 
the Sillery and Lauzon rocks, as already stated, are below and not above the Levis lime- 
stone conglomerates and graptolitic slates and sandstones, and the evidence we now have 
shews almost certainly that in this fossiliferous (Quebec group) belt are included, in a 
folded, crumpled and faulted condition, portions of all the subdivisions which, compara- 
tively undisturbed, occupy the area comprised between the great St. Lawrence and Cham- 
plain break and the archæan highlands north of the St. Lawrence and Ottawa valleys, with 
certain red, green and black argillites, which are probably even lower in the series than 
the Potsdam formation. 
This disturbed and crumpled condition of the whole group, together with the occur- 
rence at several horizons of slates and sandstones almost alike in color and texture, and the 
general absence of fossils in the older rocks, renders it almost impossible to define the sub- 
divisions of this great area of lower Paleozoic rocks. 
I have elsewhere shewn what the course of the great St. Lawrence and Champlain 
fault is, from the north-east end of the Island of Orleans to where it comes on the south 
shore of the St. Lawrence, above Quebec, at St. Antoine; thence its course southwest- 
ward is not well defined. On the Nicolet and St. Francis Rivers, it would appear to be 
about four miles more to the south-east than it is shewn on the map, and thus a consider- 
able area has been assigned to the Levis formation which certainly belongs to the Trenton 
group, and a similar mistake has been made in the vicinity of Farnham. 
Sir William Logan, when re-examining the country round Richmond in 1873, detected 
and traced for a limited distance, what has since turned out to be another great dislocation, 
quite as important in its effect on the structure. It passes through the “ transverse gap and 
the long narrow valley ” which is described page 29, of the Report of Progress, 1848, and 
again page 240 of the Geology of Canada, 1863, but the true nature of which was not then 
surmised. This valley is certainly a remarkable physical feature. There can be no doubt that 
it is due to the dislocation which here crosses the main “ Sutton and St. Joseph, or Sutton 
and Danyille” anticlinal, and lets in those so-called “ lower black slates,” at one time sup- 
posed to be older than Levis, but afterwards incorporated with it, and now proved by fossils 
