JANUARY 25, 1901.] 
had observed that the Clinton fossils of 
New York occur at higher and higher hori- 
zOns as One goes westward, and by this ob- 
servation he was led to correct some pre- 
vious errors of correlation. He placed the 
crest of the fold farther west than is ordi- 
narily done, and made the upheaval later 
than the close of the Ordovician and earlier 
than the Hamilton, whose shale goes un- 
conformably over the strata on the flanks. 
At the conclusion of the paper the Society 
adjourned for lunch. On reassembling the 
program was continued as follows: 
The Knoydart Formation in Nova Scotia—a bit 
of the ‘ Old Red Sandstone’ of Europe: H. 
M. Amt, Ottawa. 
The presence of such genera as Pteraspis, 
Pierygotus Onchus, ete., in the red marls, 
shales and calcareous breccias (?) of Mc- 
Arras Brook in Antigonish and Pictou 
counties, Nova Scotia, indicates the base of 
the‘ Old Red Sandstone’ of Great Britain. 
The paper discussed the relations, paleon- 
tological and stratigraphical, of this impor- 
tant formation in the sequence of Devonian 
strata in eastern Canada. The result of 
observations made by Mr. Hugh Plebden, of 
‘the Canadian Geological Survey, as pub- 
lished on this subject, together with im- 
portant notes by Mr. A. Smith Woodward 
and Dr. Henry Woodward, of the British 
Museum, was embodied in the paper. 
The names applied by Mr. Ami to the 
several formations of this section are the 
following : 
The Silurian of the Arisaig Coast of 
Nova Scotia is divisible into at least four 
distinct geological formations, and includes: 
1. The Stoneham formation, consisting for 
the most part of dark red and fine grained 
shales and mudstones, holding a conspic- 
uous, lamellibranchiate fauna, of which 
Grammysia Acadica, Billings is a well-known 
species, together with a number of inter- 
stratified, more or less thin, calcareous 
SCIENCE 
135 
bands, holding brachiopods, gastropods, 
trilobites and ostracods in abundance. 
2. The Moydart formation consisting of 
more or less heavy bedded, light greenish- 
gray and rusty weathering, calcareous 
strata, in which the author’s ‘ Red Stratum’ 
occurs—holding brachiopods, cephalopods, 
crinoids and gasteropods. 
3. The McAdam formation consisting for 
the most part of impure, black, carbona- 
ceous, at times splintery shale, holding a 
lamellibranchiate fauna, graptolites, etc. 
4. The Arisaig formation including buff- 
weathering, fine grained and compact mud- 
stones and shales, holding corals, chiefly 
Streptoplasma and brachiopods, gastropods 
and trilobites. 
5. Knoydart formation red shales and sand- 
stones and caleareous bands, holding pter- 
aspidian and ostracoderm fishes and crus- 
taceans, referable to the Cornstone or lower 
Old Red Sandstone of Great Britain. It 
immediately overlies the Silurian strata at 
Arisaig, but no actual contact has been ob- 
served. 
H. §. Williams inquired about the igne- 
ous rocks at the top and in further detail 
regarding the Knoydart formation. Mr. 
Ami replied that igneous rocks were pres- 
ent. The strata had been mapped as upper 
Devonian, but that they really were lower 
Devonian and possessed a pronounced Si- 
lurian facies. The whole series is much 
more closely related to the British fauna 
than to that of Anticosti. 
A Depositional Measure of Unconformity : 
CuHAarutes R. Keyes, Des Moines, Lowa. 
The paper was read by W. B. Scorr. 
The great unconformity at the base of 
the Coal Measures in the upper Mississippi 
Valley was briefly characterized in its vari- 
ous aspects. The enormous thickness of 
Coal Measures in Arkansas and Indian Ter- 
ritory finds adequate explanation in the an- 
cient geographic development. The recent 
