OEGANISMS IN ACADIA. 143 



Leperditia remarkable for their thick tests and pitted surfaces, and six species of brachio- 

 pods of the genera, Acrothele, Acrotreta, Liunarssouia and Liugulella. 



These sandstones are followed by fifty feet of comparatively barren dark grey sandy 

 shales, and they by thirty feet of hard, purple-streaked sandstones (the streaks due to 

 oxide of iron), in which occur an Agraulos of the form of Arionellus primœvvs of the 

 bed b in Sweden, and the hyalithoid shell, Diplotheca, as well as numerous tracks of 

 Psammichnites. The olive grey shale, thirty feet thick, above the sandstone, is com- 

 paratively barren, but has yielded the two species of Beyrichona, a genus which has 

 points of resemblance to Aristoze of Barraude. The upper bed of b, twenty feet thick, 

 has numerous shells of the genera Acrothele, Lingulella and Linnarssonia, and worm 

 burrows, and the brachiopods are the same as those found in the Paradoxides beds above. 



In treating of the equivalency of these several beds of the Lower Cambrian, owing to 

 the scantiness of the faunas, the comparison, bed for bed, cannot be made with the same 

 confidence as where an abundant fauna, makes an exact comparison easy. Hence the 

 physical aspect of the beds must necessarily be largely depended on in making these 

 comparisons. This affords good indications in basins so close to each other as these, but 

 even here may not be used with entire confidence. It may, for instance, be observed 

 that Band a, in the basin of Long Reach, Caton's Island, etc., is only about twenty feet 

 thick, and Band b, 200 i'eet thick, while at Hauford Brook the corresponding bands are 

 respectively 200 and VlQ feet thick. Band a is a shallow-water and beach deposit, and 

 Band b was formed in deeper water, which gave opportunity for the growth of calcareous 

 organisms ; and there is a possibility that part of Band b of King's County (Long Reach) 

 basin may be contemporary with the i;pper part of Baud a of the St. John basin, and 

 that Obolus pulcher, which we here represent as being of the same age as Hipponicharion 

 and the Leperditiœ, may in reality be somewhat older. This may not be a matter of any 

 importance, as the range of both sets of organisms may be found to be greater than it is 

 now known to be, but I direct attention to the actual facts. 



In summing up the facts bearing on the comparative age of this part of the Cambrian 

 rocks in Acadia we get no aid from the typical genera of this horizon, Olenellus and 

 Mesonacis, but the Acadian rocks contain other genera of this fauna which serve to fix 

 their age with a certain degree of accuracy. Some of these genera, however, are such as 

 may have a wider range of existence in time than the trilobites, and therefore are not of 

 of the same homotaxial value. The trilobites that do occur are not so definitive as some 

 others. 



ACADIA. SWEDEN AND RUSSIA. 



Species. Horizon. Species. Horizon. 



St. John Gr. 



Agraulos articephalus 16 Arionellus primEevus ". 16 



EUipsocephalus, »p 16 E. polytomus 1 c 



Volborthella tenuis Ih V. tenuis Blue clay 



Obolus pulcher, m. sp 16 Lingulella favosa 1 a - 



Baml series 



Obolus (?) major, n. sp 2 6 Mickwitzia monilifera la' 



Platysolenites antiquissimus 2 6 P. antiquissimus Blue clay 



Volborthella tenuis 2 6 V. tenuis Blxie clay 



