60 



A description of the orientation features in the brachiopods of the 

 next assise has been given on a previous page. There remains to record 

 the result of observations on the fossils of the highest Etcheminian 

 assise E. 3 /. 



Orientation of ORIENTATION in the valves of brachiopods in several small slabs from 

 Assise E. 3 /. tne Assise E. 3 /at Dugald brook and Indian brook. 



(Gillis' branch). 



A marine From the above observations and records it will be seen that there 



current tra- . i > * , , PIT i i 



versed Indian was quite a decided orientation of the valves or the brachiopods in a 

 brook valley 

 in Cambrian 

 time. 



Conditions of 

 entombment 

 of fossils in a 

 tidal estuary. 



fixed direction in all the Etcheminian assises of Indian Brook valley, 

 wherever these valves were in sufficient abundance to afford means of 

 determining their attitude. Had the orienting current influenced the 

 valves of only one or two horizons, or had these valves borne conflict- 

 ing testimony at different levels, there might have been some question 

 as to the cause of the phenomenon, but in view of the constant orien- 

 tation here in a fixed direction thoughout Etcheminian time we can 

 only conclude that this valley is of pre-Cambrian origin, and guided 

 the course of a marine current that traversed it in a north-easterly 

 direction. 



It is a question for consideration whether this current was an ordin- 

 ary shore current along the coast, or a tidal current. The following 

 are some conditions which bear upon the latter hypothesis. 



It may be surmised that entombment in the mud of a tidal estuary 

 would take place chiefly on the ebb-tide. On the flood-tide the waters 

 coming from the open ocean would arrive free from sediment, but with 

 the waves beating on the freshly submerged shore, and the possible 

 contribution of river sediment coming into the head of the tidal estu- 

 ary, the returning water, retiring with the ebb-tide, would carry a load 

 of sediment to spread over the sea-bottom and bury such animals as 

 had reached the limit of their vitality, or were unable to free them- 



