1. Introdiictory Remarks. 



As far back as aboiit fifty years ago, it was noticed by 

 WAHLENBERfi and Dalman that the alum-scliists of Sweden con- 

 tain a peculiar fauna, totally diiierent from that of the overlying 

 strata. ^) The iniportance of this geological horizon was not, 

 liowever, iully appreciated, until Mr. Barrande pointed out its 

 wide range, and showed that the oklest fossil-bearing strata of 

 Boheniia contained a fauna analogous to that of the Swedish 

 akun-schists. The "Primordial zone", of which these Swedish 

 and Bohemian deposits were made the types, was soon recog- 

 nized in several countries, but its classification has not been 

 worked out in detail until Avithin the last few years. 



The first atterapt to establish subdivisions in the Primordial 

 zone of Sweden was made by Professor Angelin, by Avhom it 

 was divided into two "regions", regio A. Olenorum and regio 

 B. Conocorypharum. -) Their stratigraphical relation to each 

 other was not made out, but the latter, having a richer fauna, 

 was eonsidered the younger. The regio Conocorypharum was 

 stated to occur only at Andrarum in Scania and in the island of 

 Bornholm, while all the Primordial strata of the other Swedish 

 provinces were, as a whole, referred to the regio Olenorum. 



When I began to study in detail the Primordial zone of 

 Westrogothia, I soon found that the Oleni were exclusively 

 confined to the upper portion of the alum-schists, and that the 

 lower contained quite difterent genera, as Paradoxides and Co- 

 nocoryphe. I therefore »proposed to restrict the regio Olenorum 

 to the upper portion of the alum-schists and refer the lower 

 portion, in which no Oleni occur, to the regio Conocorypharum, 



*) See. for instance. Wahlenberg, Geologisk afhandling om Svenska jor- 

 dens bildnine, Upsala 1824, pp. .38. .52, etc; Dalman, K. Vet. Akad. Handl. 

 1826, p. 150. 



^) Palaeontologia Scandinavica, p. III, IV. 



