TRANSACTIONS OF SECTION C. "55 
sigmoidal curves, the same curves practically which would be followed by the 
outcrop of intermediate horizons of the crust in any ground-plan of the unit-area 
of torsion. 
Among the tectonic phenomena which may be demonstrated in a unit-area of 
torsion are the arrangement of the horizons of the stratigraphical succession in 
elliptical whorls set at right angles, the formation of crust-folds in opposite or 
sometimes intersecting arcs, and of faults in ‘fault-polygons’ and ‘bundles,’ the 
cross-transferences of rock-material], the fan-structure of cross-arches, and the dis- 
position of consolidated fault-rock in sigmoidal bands. ‘These phenomena become 
much more complicated when the unit-area is considered as part of a much larger 
area of torsion, since the varying magnitudes and varying shapes of the wave- 
forms in a large region of cross-arches and troughs necessarily cause all kinds of 
local structural peculiarities. 
Sigmoidal curves limit the great mountain-masses and troughs of the Alpine 
system, and are associated there (ex. Prattigau, Salzkammergut, &c.) with all the 
above-mentioned phenomena of crust-torsion. What is designated a Central 
Massive or a major Trough in the Alpine mountain system really represents a very 
large wave-form, which bears upon its surface a number of smaller wave-forms 
represented by the subordinate cross-arches and covered troughs in each great 
Massive or Trough. 
2. Adjourned Discussion on Wave Phenomena, See p. 748, 
3, Report on the Ossiferous Caves at Uphill, See Reports, p. 402. 
4, Report on Erratic Blocks of the British Isles, See Reports, p. 398. 
5. On the Subdivisions of the Carboniferous System in certain portions of 
Nova Scotia. By H. M. Amt, IA., F.GS., of the Geological Survey 
of Canada, 
Considerable discussion has arisen of late in Canada regarding certain sediments, 
near the summit of the Paleozoic columns. No doubt exists as to the proper and 
natural succession, but whether the red sandstones and shales and conglomerates 
of the Union formation, and the grey and dark carbonaceous shales and sandstones 
of the Riversdale formation of Pictou, Colchester and Cumberland counties of 
Nova Scotia should be classed as Carboniferous or Devonian was the problem 
which presented itself to Canadian geologists. ; 
From a careful collection of paleontological material in the formations in 
question, the writer has been able to satisfy himself that the Union and Riversdale 
stratahold a flora and a fauna which in every essential feature are truly Carboniferous. 
The plants obtained were submitted both to Professor David White of Washington, 
and to Mr. Kidston of Stirling, Scotland, and they both recognise a distinctly 
Carboniferous flora. 
The Ostracoda were examined by Professor T. Rupert Jones, F.R.S., who 
reports that the forms have a decidedly Carboniferous facies. The wing of a large 
neuropterous insect is referred to a Carboniferous genus by Professor Charles 
Brongniart. Reptilian and fish remains, tracks and trails of the former all serve 
to point to post-Devonian times. 
To assign such a fauna and a flora as are found in the Union and Riversdale 
formations of Nova Scotia to the Devonian period would be contrary to the con- 
sensus of opinion and generally accepted inferences of the leading geologists in 
the world, and contrary to the principles of classification. 
The various life-zones of these two formations, as well as the cltaracters of the 
sediments due to the conditions in which they were deposited, serve to unite them 
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