88 THE nuRONiAN. 



same. The peculiar fossils, however, Aspidella and Arenicolites^ allied 

 to A. spiralis^ discovered by Murray iu the Upper Iluronian of New- 

 foundland and described by Billings, have not yet been recognised in 

 New Brunswick. 



The Coldbrook series is remarkable for the abundance in it of 

 felsites, felsltic breccias, porphyry, diorite, and other crystalline or 

 cryptocrystalline rocks, which, though stratified, are evidently of 

 volcanic origin, and if such rocks are to be considered as everywhere 

 of this age, the classification of the older rocks of Acadia would be 

 greatly simplified. It is evident, however, that we must separate 

 the Mascarene series, and other rocks of this character, with Upper 

 Silurian fossils ; and there is no good evidence that the Cobequid 

 series and its equivalents in Pictou and elsewhere are older than the 

 Lower Silurian. There seems, however, good reason to class as 

 Huronian, or at least as Lower Cambrian, the rocks of the Boisdale 

 Hills in Cape Breton, which Mr Fletcher finds to underlie the fossili- 

 ferous Cambrian of that region, and which are more quartzose and 

 micaceous than the rocks of the Cobequid series. It is not impossible 

 that rocks of this age may also occur in the vicinity of the Cambrian 

 beds found at Mire. AA'e may also conjecturally class as Iluronian 

 the chloritic rocks of Yarmouth. 



I may repeat here my conviction, founded on the comparison of 

 large suites of specimens from Newfoundland, and from Nova Scotia 

 and New Brunswick, as well as from the typical localities in Lake 

 Huron, that volcanic and trap-ash rocks of various composition were 

 in process of deposition from the Iluronian to the Upper Silurian 

 inclusive, and that they cannot be distinguished in hand specimens. 

 It is only by considerations based on stratigi'aphy and fossils that 

 these rocks can be ultimately classified with certainty. Unfortunately, 

 in many cases, decisive evidence of these kinds is not easily obtained, 

 and in the meantime our classification has to remain to a great extent 

 conjectural. 



13. THE LAURENTIAN. 



These rocks, as they occur near St John, New Brunswick, have 

 been arranged by Messrs Bailey and Matthew, in their recent 

 Eeports, in a Lower and Upper series.* The former consists, in 

 ascending order, of gray gneiss, red and gray gneiss, and dark-gray 

 gneiss, with chloritic gneiss and diorite. The latter consists of 

 limestone, with graphite and serpentine, gray quartzites and diorite, 

 gray slates and limestones with diorite. In one of the Upper Lime- 



* Geol. Reports, 1871, etc. See also Note \l: 



