RlSsUM^, AND GENERAL msCUSSION. 



551 



a matter of coursej that tho series thus designated can only be separated 

 into sub-sjstema on purely lithological grounds : if they arc fossilif- 

 crous, as held by the Canada Survey, then it is equally clear that any 

 subdivisions proposed for them should have a palxoutological basis. 



It is true that the Canada Survey did, for a time, uphold tbe idea that 

 the Laurentian and Iluronian were to be separated from each other oa 

 fossilifcrous grounds, namely, that the one contained the Eozoon and the 

 other did not; but tliis rather unsatisfactory basis of classification was 

 soon abandoned. Later, it has been maintained by Mr. Murray, of the 

 Newfoundland Survey,* that certain peculiar forms, supposed to be of 

 organic origin, were characteristic of the Iluronian of that region. Of 

 one of these supposed fossils (the Aspidella) the palaeontologist of the 

 survey could only say that *'its general aspect is that of a small Chiton 

 or Patella ^^ ; but he hastens to add, that ''it is not probable, however, 

 that it is allied to either of these gcnera/'f To us, the general aspect 

 of the fossil in question, as figured by Mr. Billings, is that of a concre- 

 tion intersected by small irregular cracks, and much more resembling 

 the so-called Septaria than anything organic. 



Specimens of Aspidella sent us by Mr. Murray, however, do not 

 resemble in any reapect tho fossil figured by Mr. Billings. There are 

 several indistinct impressions on the fragment of rock, neither of them 

 like that fossil, and none of them necessarily of organic origin, at least 

 so far as we are able to discover. They look more like spray markings 

 than anything else with which we are able to compare them. 



Of equally dubious character is the other of these so-called fossils, by 

 which it is believed by the Canada geologists that the Huronian can be 

 separated from the Laiu-entian. We refer to the Arenicolites sjnralis, 

 mentioned by Mr. Billings in the ''Palasozoic Fossils," t of wliieh no de- 

 scription is given by him, it being only said to "occur near St. John's, 

 in the Huronian." It is added, however, that "a more detailed descrip- 

 tion will be given hereafter." Tlie real nature of this supposed fossil has 

 already been sufficiently indicated by Dr. Wadsworth.§ Whether tho 

 Arenicola didyma, and the Arenicolites sparstis, of Salter, are or are not of 

 organic origin, it is unnecessary lierc to inquire. That palaeontologist con- 

 siders them '* burrows of annelides." We sec little resemblance between 

 these forms as figured by him and the Arenicolites of the Canadian Survey. || 



* See ante, p. 380. 



+ Geological Survey of Canada, PaLTOzoic Fossils, Vol. II. Part I. p. 77. 

 t I. c, p. 77. § Seience, I. 89. 



11 A large number of specimens of the Arenicolites were collected by Dr M^ads- 

 worth in the vieiniiy of St. John's. 



