A few years later, my attention was attracted to this species by specimens presented to me by Mr. Carpenter, a missionary on the Labrador coast, and which Mr. Billings kindly permitted me to compare with his specimens in the Museum of the Geological Survey, collected by the late Mr. Richardson, at L'Anse à Loup, in Labrador, in what were then called Lower Potsdam rocks. Slices of the specimens were made for the microscope, when it appeared that, though they had the general aspect of turbinate corals, like Petraia, etc., they were quite dissimilar in structure, more especially in their porous outer and inner walls and septa (see Fig. 5, p. 35). Yet they could scarcely be referred to the group of porous corals known in much later formations and in the modern seas. Nor could they be referred with much probability to Sponges, as they were composed of solid calcareous plates, which, as was evident from their textures, could not have been originally spicular. One seemed thus shut up to the conclusion that their nearest alliance was with Foraminifera, and if so, they were very large and complex forms of that group, consisting of perforated chambers arranged around a central cavity. I accordingly mentioned them in this connection in 1875, not as closely related to Eozoon, but as apparently showing the existence of very complex foraminiferal forms in the Lower Cambrian. The specimens thus noticed were altogether calcareous, and were of the species named _A. profundus_ by Mr. Billings. He had, however, referred to the same genus silicified specimens from a later formation, the Calciferous (Upper Cambrian) at Mingan, under the name _A. Minganensis_, which were subsequently found to be associated with spicules resembling those of lithistid sponges, and which proved to be very different from the Lower Cambrian form, and are now referred to a different genus. The subject had thus become involved in some confusion, and was left in this state by Mr. Billings on his death. I therefore asked my friend, Dr. Hinde, of London, to re-examine my specimens, and at the same time those of the Geological Survey were placed in his hands by Mr. Whiteaves. Hinde also obtained specimens from Lower Cambrian rocks in Sardinia, where they seem to be abundant, and from Spain. He states the results of his examinations very fully in a paper in the Journal of the _Geological Society of London_.[58] He retains the original name for the older and calcareous form from L'Anse à Loup, separating from it, however, another form, _A. Atlanticus_ of Billings's, which is destitute of distinct radiating septa and acervuline, like the lower part of _A. profundus_. This he names _Spirocyathus_. The Mingan species he places with Sponges under the generic name, _Archæoscyphia_. In this Walcott substantially agrees with Hinde in his "Memoir on the Lower Cambrian Fauna." Both seem to refer Archæocyathus to corals, though admitting its very exceptional and anomalous structure.