62 



McLeod brook was proportionally lower in Etcheminian times than 

 now ; otherwise there would not be a sufficiently open passage for the 

 flow of the current from one basin to the other. 



All along the Indian brook basin the Etcheminian sediments are 

 replete with material derived from the rocks of the complex pre-Camb- 

 rian along the sides of that valley and the Coldbrook volcanics with 

 which this was overlaid. The basin was bordered with a ridge of these 

 rocks all along its north-western side ; and from the exactness with 

 which the marine current was directed along this basin it seems clear 

 to me that there was a complementary pre-Cambrian ridge along the 

 south-eastern side of the basin as there is now on that side of the 

 valley. Both ridges were probably of greater elevation in Etcheminian 

 times than now. 



In the course of the writer's observations in Cape Breton, no other 

 opportunity to test the orientation of the Cambrian brachiopod was 

 met with, except at Young point at the north-east end of the Bara- 

 chois basin, and the result here was surprisingly different from that 

 obtained on Indian brook. 



Orientation of The fossils at Young point are supposed to belong to the lower part 

 Lingulellasat . _. . . ,. , FF . ,. . ^ 



Young point f Division 2, a zone trom which no orientation data were obtained on 



that rf"l dl m I n( ^ an brook. The fossils here are mostly Lingulellas of the species 

 brook. L. Seluiyni, and the upper side of the layers (though the beds stand at 



a rather high angle) was satisfactorily determined by finding from 

 eighty to ninety per cent of the shells with the hollow side up. This 

 peculiarity in the attitude of shells buried in the mud of the Cambrian 

 terranes is noticeable in many of the assises of the Cape Breton areas. 

 Two causes may have helped to produce it. Gravitation causing the 

 shell to sink to the bottom, would be best served by the shell present- 

 ing the side of least resistance, i.e., the rounded side to the bottom. 

 To this would be added the lifting power acting on the upper (inner) 

 surface of the valves, of the decomposition of the organic matter in the 

 fleshy parts of the body, producing a buoy, that would sustain the 

 shell with the inner side uppermost while sinking to the bottom. 



The fossils described in the following table were found in a number 

 of seams of sandy shale in the lower part of the section and were in 

 a thickness of about a foot of this shale. The record of orientation 

 was made in reference to the cardinal points, and the shells of both the 

 upper and the under side of each slab were noted. 



