It may be proper to mention here the alleged Pulmonifera of the genus _Palæorbis_ described by some German naturalists. These I believe to be worm tubes of the genus _Spirorbis_, and in fact to be nothing else than the common _S. carbonarius_ or _S. pusillus_ of the coal formation. The history of this error may be stated thus. The eminent palæobotanists Germar, Goeppert and Geinitz have referred the _Spirorbis_, so common in the Coal measures to the fungi, under the name _Gyromyces_, and in this they have been followed by other naturalists, though as long ago as 1868 I had shown that this little organism is not only a calcareous shell, attached by one side to vegetable matters and shells of mollusks, but that it has the microscopic structure characteristic of modern shells of this type.[139] More recently Van Beneden, Cænius, and Goldenberg, perceiving that the fossil is really a calcareous shell, but apparently unaware of the observations made in this country by myself and Mr. Lesquereux, have held the _Spirorbis_ to be a pulmonate mollusk allied to _Planorbis_, and have supposed that its presence on fossil plants is confirmatory of this view, though the shells are attached by a flattened side to these plants, and are also found attached to shells of bivalves of the genus _Naiadites_. Mr. R. Etheridge, jun., of the Geological Survey of Great Britain, has summed up the evidence as to the true nature of these probably brackish-water shells, and has revised and added to the species, in a series of articles in the _Geological Magazine_ of London, vol. viii. [139] "Acadian Geology," 2nd edition, p. 205. The erect trees of Coal Mine Point are rich in remains of Millipedes. The first of these (_Xylobius Sigillariæ_), which was the first known Palæozoic Myriapod, was described by me from specimens found in a tree extracted in 1852, and this, with a number of other remains subsequently found, was afterwards placed in the hands of Dr. Scudder, who has recognised in the material submitted to him eight species belonging to three genera (_Xylobius_, _Archiulus_, and _Amynilyspes_). These animals in all probability haunted these trees to feed on the decaying wood and other vegetable matter, and were undoubtedly themselves the prey of the Microsaurians. Though these were the earliest known, their discovery was followed by that of many other species in Europe and America, and some of them as old as the Devonian.[140] [140] The two first-named genera from the erect trees, according to Scudder, belong to an extinct family of Millipedes, which he names Archiulidæ, and places with other Carboniferous genera in the order _Archipolypoda_. The third belongs to family Euphoberidæ. Proc. R. S. of London, 1892.