_Calamopitys_, as the generic designation is here employed, is confined to central Germany and Kentucky and occurs in Upper Devonian and Lower Carboniferous strata. There is, however, some doubt as to the exact geological horizon of the rocks in both countries though in neither case is there any question of an horizon higher than Lower Carboniferous. Certain specimens from the Lower Carboniferous of Scotland described by Scott[496] as species of _Calamopitys_ have been made by Zalessky the type of a new genus, _Eristophyton_, and are dealt with under that name. _Kalymma._ Unger. _Kalymma grandis_ (petiole of _Calamopitys_). Under the generic name _Kalymma_ Unger described specimens from Thuringia of Upper Devonian age which he assigned to two species, _K. grandis_ and _K. striatum_. Solms-Laubach has shown that _Kalymma_ is not an independent stem as Unger believed but a petiole of _Calamopitys_, and this has been confirmed by Scott and Jeffrey who found a leaf-base with the _Kalymma_ type of structure in connexion with a piece of _Calamopitys_ stem, probably _C. americana_. An examination of a section (2·3 cm. broad) of Unger’s _K. grandis_ in the collection of the Geological Survey enables me to confirm the conclusions recently published by Scott and Jeffrey. The best specimens of _Kalymma_, which appear to be identical in essential features with Unger’s type-species, are from Kentucky, some from the Genessee shales of Upper Devonian age and others from beds (Waverley shales) believed to be Lower Carboniferous. Through the kindness of Prof. Bower I have had an opportunity of examining sections from the older horizon in his possession. The transverse section reproduced in fig. 456 has a diameter of 3·8 × 2·2 cm.[497]: on one side the radially placed plates of stereome are clearly shown, and in the outer portion of the ground-tissue is a ring of vascular bundles varying in size and shape but with a general tendency to a radially elongated form. The ground-tissue consists of homogeneous parenchyma: in one place I noticed what appeared to be a large secretory canal, but secretory tissue, generally at least, is unrepresented. The xylem is composed of imperfectly preserved elements, which appear to have scalariform pits; spiral protoxylem strands, embedded in the metaxylem as two or four groups, occur near the ends of the long axis of the bundle and in some cases also near the centre. The phloem probably surrounded the xylem, though it is not certain whether the arrangement was collateral or concentric: there are no secondary-xylem tracheids, though in some places I noticed a tendency to a radial disposition of cells at the periphery of the vascular tissue simulating an early stage of secondary growth. Unger’s second species _Kalymma striata_ is characterised by an arrangement of the bundles similar to that in a petiole described by Scott and Jeffrey as _Calamopteris Hippocrepis_ which differs from _Kalymma_ in the partial substitution of bands