I think it proper to state, in reference to Dr. Dallinger's footnote on the recent paper of Mr. Gregory, that it must not be inferred from it that Mr. Gregory had access to my specimens from Madoc and Tudor, though he no doubt had excellent material from the collections of the Canadian Geological Survey. It might also be inferred from this note that I have regarded the Madoc and Tudor specimens as "Lower Laurentian." The fact is, that I was originally induced in 1865, by the belief of Sir W. E. Logan at that time that these rocks were representatives in a less altered state of the middle part of the Laurentian, to spend some time at Madoc and its vicinity in searching for fossils, but discovered only worm-burrows, spicules, and fragments of Eozoon, which were noticed in the _Journal of the Geological Society_ for 1866. (The more complete specimen from Tudor was found by Vennor in 1866.) On that occasion I satisfied myself fully that the beds are much older than the Cambro-Silurian strata resting on them, unconformably; but I felt disposed to regard them as more probably of the age of some parts of the Huronian of Georgian Bay, which I had explored with a similar purpose under Logan's guidance in 1856. [In my subsequent notice of the Tudor specimens in "The Dawn of Life," in 1875, I referred to their age as "Upper Laurentian or Huronian"; and I may add, that while it is certain that the beds containing them are pre-Palæozoic, their place in the Eozoic period is still not precisely determined. Work is, however, now in progress which it is hoped may finally settle the age of the "Hastings group" and the old rocks associated with it. I may add that the specimen of Cryptozoon discovered by Mr. Chambers, and of which a portion is represented in the Frontispiece, seems to me to throw a new light on the Tudor specimen. It shows in any case the survival of Cryptozoa similar in form and general appearance to that specimen, as late as the Cambro-Silurian or Ordovician.] * * * * * H. Notes to Appendix, December, 1896. While this work was going through the press, I have received the Report of the U.S. Geological Survey for 1894-95, containing the elaborate Memoir of C. R. Van Hise on the pre-Cambrian Geology of North America. It is a very valuable contribution to the literature of this difficult subject, and will constitute a standard book of reference: though I think the use of the term "Algonkian" for groups of beds which are in part basal Palæozoic and in part Eozoic or Archæan is to be deprecated, and scarcely sufficient importance is attached to the labours of the early Canadian explorers in this field.