138 Discoveries in the St. John Group. 



(th3 system containing Eozoon) and the Cambrian. The 

 organic form which occurs in this Intermediate system was 

 described by the late Mr. E. Billings of the Canadian Geological 

 Survey, who appears to have thought it a representative of the 

 Gasteropods (Sea-snails, etc.) and gave it the name of Aspidella 

 terranovica. It is a curious patelliform object, which Mr. Bill- 

 ings was unable to refer to any known genus or family, so that its 

 bearing on the question of the origin of the Lower Cambrian or 

 Acadian fauna of the St. John group is somewhat problematical. 



In the Acadian fauna of the St. John group, notwithstanding 

 its antiquity, we do not have the ultimate source of organic life, 

 but, on the contrary/ an assemblage of animals already greatly 

 differentiated and adapted to the conditions under which they 

 existed. At the time when the Acadian fauna nourished, 

 there may also have been other areas on the globe occupied by living 

 beings, for when we consider the place and mode of occurrence of the 

 species of the St. John basin, belonging to Division or Series 1, 

 both described and undescribed, it is clear that there were three 

 successive irruptions of living forms into this area, all of Lower 

 Cambrian types, and all strictly within the limit upward of the 

 Paradoxidean zone. Each of the three sets of organisms in these 

 beds contains a large proportion of distinct species, with a smaller 

 number of identical species. The latter serve as connecting links 

 to bind these several sub-faunas together as one connected whole. 



Before describing the three assemblages of organic forms that 

 are found in the lower part of the St. John group it may be well 

 to give a brief statement of the nature and order of the beds in 

 which they occur. The St. John group has been divided in 

 six principal masses of strata, designated as Divisions (^Series) 

 0, 1, 2, 3, 4 and 5. Of Division 0, it may be said that no organic 

 remains have been found in it ; but in Division 1 is found the fauna 

 described by Professor Hartt and others. This fauna is not found 

 at the base of Division 1, but in one of its middle members. 

 Division 1 at St. John has been described as consisting of 

 four bands of strata, differing in the nature of the sediments, and 

 designated respectively, in ascending order, as a, b, c, and d. The 

 band a is barren, and c contains the species already described; 

 but both b and d are now found to have each their own peculiar 

 assemblage of species. 



