_Knorria._--To this genus the authors of the Fossil Flora of Great Britain referred those stems which have projecting leaf-scars, arranged spirally. The beautiful specimen figured as _Knorria taxina_, _Lign. 41, fig. 2_, closely resembles a young branch of Yew (_Taxus_), and perhaps might be more correctly named _Taxites_. _Bothrodendron and Ulodendron._--These genera, together with _Megaphyton_, are stems of a very remarkable character, and are easily distinguished by the vertical rows of large and distant scars. The two first have two series of very deep oval depressions on opposite sides of the stems, arranged alternately in the specimens I have examined: from the size and form of these obliquely-oval cavities, it is supposed that they were formed by the attachment of cones, and not by petioles; but their real nature is involved in obscurity.[115] [115] Figured in Bd. pl. lvi. In _Megaphyton_, the large ovate scars indicate the attachment of deciduous branches or gigantic leaves, which did not grow all round the stem, but in a regular order of superposition on each side.[116] [116] Figured in Pict. Atlas, pl. xxv. [Sidenote: ASTEROPHYLLITES.] Asterophyllites.--I shall conclude this notice of some of the most characteristic trees of the Carboniferous Flora, with an account of a tribe of plants whose remains are so common in the coal-shales and grits, that there are but few large slabs with vegetable remains that do not exhibit examples of the elegant verticillate foliage of one or more species. The term _Asterophyllites_, (expressive of the star-like form of the leaves,) applied to this family by M. Ad. Brongniart, includes several fossil plants which are known to geologists under different generic names; the following concise account may be useful to the student.[117] [117] Consult _Tableau des Genres de Végétaux Fossiles_, par M. Ad. Brongniart. Diet. d'Hist. Nat. Paris, 1849. 1. _Calamodendron._--These are arborescent stems, ligneous internally, and covered with a smooth carbonaceous crust, without regular longitudinal striæ, and not articulated; but the woody axis covered by this bark is deeply striated and articulated, resembling in this respect the true Calamites. These stems have a large central pith, or medullary column, surrounded by a ligneous zone, which is formed of radiated bands, without circles of growth: the structure of the carbonized bark is unknown. 2. _Asterophyllites._--These are supposed to be the branches and foliage of the stems above described. 3. _Sphenophyllum._--Plants, differing in the form of the leaves, but analogous in structure and mode of fructification to the Asterophyllites. 4. _Annularia._--Herbaceous aquatic plants, distinct from the preceding. 5. _Volkmannia._--These fossil plants are Asterophyllites in fructification.