2 NOTES ON CONCRETIONS 



Concretions are most commonly spheroidal, or nearly so in> 

 shape, and range in size from that of a grain of sand to twenty 

 and thirty feet in diameter. 



1. On the coast of Arisaig, N. S , in the argillaceous slates, 

 and shales of the Clinton formation, slightly flattened spher- 

 oidal forms are abundant. Two of these, about two feet in 

 diameter when broken through the centre, showed no concentric 

 layers or nuclei, while many others, varying in size from the 

 eighth of an inch to two inches in diameter, contained invariably 

 a nucleus ; sometimes a grain of sand, but generally the brachio- 

 pod, Lingula oblonga, Hall. 



2. The largest concretions seen by the writer were found in 

 the Fox Hill and Pierre shales and clays of the North-West,, 

 and a very interesting exhibition of giant forms may be seen 

 three miles north of Irving station-house on the Canadian 

 Pacific Railway. Here, huge boulder-like spheroidal and ovoid 

 concretions once held in the rocks but removed by great 

 denudation (probably in the glacial epoch, for glacial striae are- 

 seen on some of the flat beds), stand out in bold relief, resting 

 on the flat and upturned edges of shales and sandstones ; and 

 on the top of one of them, about twenty feet high, an eagle had 

 built its nest of buffalo-bones and the roots of the wild sage, for 

 want of a more elevated situation, which does not occur in this- 

 locality. 



In composition they appear to be chiefly argillaceous -and 

 calcareous sandstones. Many of them have fallen to pieces, and 

 the debris shows that they have been formed in layers which 

 increased in thickness from the centre outward. Portions of the- 

 beds from which they were derived were found enclosed in 

 several of them, and the stratified pieces of the bed-rock were 

 found to be prolific in fossils. Among the genera and species 

 found in these were : Lingula nitida ; Protocardia subquadrata ;. 

 Liopistha undata, etc. 



3. Mr. R. G. McConnell, of the Geological Survey, describes- 





