With reference to the first of the above heads, I have now to state that it seems quite certain that the upper and younger portions of the masses of Eozoon often passed into the acervuline form, and the period in which this change took place seems to have depended on circumstances. In some specimens there are only a few regular layers, and then a heap of irregular cells. In other cases a hundred or more regular layers were formed; but even in this case little groups of irregular cells occurred at certain points near the surface. This may be seen in plate III. I have also found some masses clearly not fragmental which consist altogether of acervuline cells. A specimen of this kind is represented in fig. 31. It is oval in outline, about three inches in length, wholly made up of rounded or cylindrical cells, the walls of which have a beautiful tubular structure, but there is little or no supplemental skeleton. Whether this is a portion accidentally broken off from the top of a mass of Eozoon, or a peculiar varietal form, or a distinct species, it would be difficult to determine. In the meantime I have described it as a variety, "_acervulina_," of the species Eozoon Canadense.[AF] Another variety also, from Petite Nation, shows extremely thin laminæ, closely placed together and very massive, and with little supplemental skeleton. This may be allied to the last, and may be named variety "_minor_." [Footnote AF: _Proceedings of Geological Society_, 1875.] [Illustration: Fig. 31. _Acervuline Variety of Eozoon, St. Pierre._ (_a._) General form, half natural size. (_b._) Portion of cellular interior, magnified, showing the course of the tubuli.]