138 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
the Lower Rihirian nx^ks has Ixmui ohservod ... in Nova 
Scotia at (.'ape St. George, Arisais, Lochaber, and from Kerrow- 
Sane down the East River of Pictou, and north of Sunderland 
Lake." One of the stumbUng-blocks in the way of a('('<>ptin{^ 
this statement is that within the area designated by Dana no 
undoubted Ordovician rocks have been recognized. 
The geology around Arisaig has l)een well described by Wil- 
liams, whose paper contains the following statement. 
''f Ordovician deposits. — Erosion agencies appear to have worn 
wide channels out of tht; Brown's Mountain [U. Camb.] rocks 
before the later sedimentary formations were laid down. The 
coarse cross-bedded conglomerates and grits of the Malignant 
Cove formation, occuring at Malignant Cove and to the 
.south, were deposited upon the cleavage surfaces of the 
James River slates. Their deposition was evidently influenced 
by strong current action and their sedimentation characters, 
together with their general red color, suggest for these poorly 
sorted but well-worn deposits a continental origin. 
"Because of the orogenic disturbances suggested and because 
of the silicified character of its rocks, which are similar to those 
of the Brown's Mountain group, the Malignant Cove formation 
is thought to be a remnant of early Ordovician sedimentation."^ 
The Silurian rocks rest on an old rhyolite flow, and, moreover, 
are separated from the older rocks by a fault with a probable 
throw of from 3000 to 4000 feet. These structural relations are 
more fully discussed in Williams' later work,- but no essential 
part of his original statement as quoted need be amended. 
McLearn, writing more recently,^ adds nothing to our knowledge 
of the structure. 
Fletcher, who has written a good deal on this region,* scarcely 
ever described a contact in terms of conformability. 
"The Cambro-Silurian is overlain by the Silurian" is his stand- 
'Williams, M. Y. Geology of the Arisaig- A ntigonish District, Nova 
Scotia. Amer. Journ. Sci., ser. 4, vol. 34, p. 246, 1912. 
^Williams, M. Y. The Arisaig-A ntigonish District, Nova Scotia. 
Mem. Geol. Surv. Canada, no. 60, 1914. 
'McLearn, F. H. The Silurian Arisaig series of Arisaig, Nova Scotia. 
Amer. Journ. Sci., ser. 4, vol. 45, p. 126-140, 1918. 
^Fletcher, Hugh. Ann. Rept. Geol. Surv. Canada 1886, vol. 2, p. 41P, 
1887. 
