The occurrence of this and other stems of tree-ferns in marine beds has recently been illustrated by the observation of Prof. A. Agassiz that considerable quantities of vegetable matter can be dredged from great depths in the sea on the leeward side of the Caribbean Islands. The occurrence of these trunks further connects itself with the great abundance of large petioles (_Rhachiopteris_) in the same beds, while the rarity of well-preserved fronds is explained by the coarseness of the beds, and also by the probably long maceration of the plant-remains in the sea-water. In connection with this I may refer to the remarkable facts recently stated by Williamson[BL] respecting the stems known as Heterangium and _Lyginodendron_. It would seem that these, while having strong exogenous peculiarities, are really stems of tree-ferns, thus placing this family in the same position of advancement with the Lycopods and Equisetaceæ of the Coal period. [BL] "Proceedings of the Royal Society," January 6, 1887. IV.--On Erian Trees of the Genus Dadoxylon, Unger. (_Araucarites_ of Goeppert, _Araucarioxylon_ of Kraus.) Large woody trunks, carbonised or silicified, and showing wood-cells with hexagonal areoles having oval pores inscribed in them, occur abundantly in some beds of the Middle Erian of America, and constitute the most common kind of fossil wood all the way to the Trias. They have in the older formations, generally, several rows of pores on each fibre, and medullary rays composed of two or more series of cells, but become more simple in these respects in the Permian and Triassic series. The names _Araucarites_ and _Araucarioxylon_ are perhaps objectionable, inasmuch as they suppose affinities to _Araucaria_ which may not exist. Unger's name, which is non-committal, is therefore, I think, to be preferred. In my "Acadian Geology," and in my "Report on the Geology of Prince Edward Island," I have given reasons for believing that the foliage of some at least of these trees was that known as _Walchia_, and that they may have borne nutlets in the manner of Taxine trees (_Trigonocarpum_, &c). Grand d'Eury has recently suggested that some of them may have belonged to _Cordaites_, or to plants included in that somewhat varied and probably artificial group.