356 Correspondence. 
survey carefully the bottom of the fall. Contrary to Logan's section of 1861, 
there is no Trenton limestone; showing that the packs of limestone fallen 
from the top, have been destroyed and carried away. But more, there are 
no Utica and Hudson River slates, as marked at the bottom of the fall, on 
the section of Mr. Selwyn of 1884. The bottom of the fall, and to a distance 
of forty feet from the foot of the fall, is formed of the game quartzite 
rocks as the fall. (Called La^irentian gneiss by Mr. Selwyn.) Lying against 
the quartzites are gray shales, alternating with layers of marly limestone, 
without fossils dipping S. S. B. at an angle of seventy degrees. They 
belong to the City and Citadel Hill of Quebec group or Swanton slates. 
At Petit Ruisssau, west of Charlesbourg, the "landslides" of the Trenton 
over the Taconic slates can be seen at different places, specially below the 
Mill. 
At Indian Lorette the landslides are conspicuous. 
Mr. Selwyn speaks of "Mr Marcou's not very complimentary remarks in 
reference to Logan and himself." I have carefully quoted their views and 
opinions, on their three large faults of what Mr. Selwyn calls '■'supposed 
structure from Montmorency falls to the island of Orleans;" when both of 
them have passed over contemptuously, without any reference whatever, 
my observations at Montmorency, published in 1860, 61, and 62, as if I had 
never published anything on the Geology of Quebec city and its vicinity. 
Perhaps Mr. Selwyn regards it as complimentary. 
As to placing the Taconic system "on a par with the Quebec group and 
like it," Mr. Selwyn in this adds a new example of the confusion so 
persistently made, and it shows how difficult it is to establish a proper case 
for the discussion of each contested point in the stratigraphy and paleon- 
tology of the Taconic region, as well in Canada as in the United States. 
Cambridge, Mass , August 14, 1888. Jules Marcou. 
The position of the Olenelhis beds. There are circumstances which are 
more than perplexing. Such is, for example, tlie tenacity with which 
Messrs. Walcott and Ford still adhere to the opinion that the strata with 
Olenellus should be younger than the Paradoxides beds, in spite of the 
fact that, as myself, Linnarson and Brogger have shown, the former in- 
variably have their position underneath the latter ; and when so proven 
Messrs. Walcott and Ford express doubts whether our Olenellus is a true 
Olenellus! It is also most astonishing to see Mr. Walcott describe a 
great number of primordial trilobites as new genera while they are most 
nearly allied and probably often even identical with European species 
known long ago. A. G. Nathorst, 
Royal Museum, Stockholm, September 9, 188S. 
Br. Itoiniiujsr's rejoinder to Mr. CD. Walcott.* Mr. Walcott finds 
fault in my not having made an attempt to give the stratigraphic position 
of the fauna by making comparison with published sections or with the 
species of similar form that have been described from the Cambrian strata 
* Dr. Rominger's deceriptions of primordial fossils fromMr. Stephen were published 
in the July number of the Ptoc. A. of Nat. Sciences of Philadelphia, in 1887. Mr. 
Walcott's criticisms are found in Amer. Jour, ot Hcience for ?ept, 1888. 
