This generic name in the form _Pitus_ was first used by Witham[753] for some petrified pieces of large stems from Lower Carboniferous strata in the south of Scotland (Berwickshire). In an earlier paper Witham[754] gives an account of the beds on the banks of the Tweed from which the specimens of _Pitys_ and other plants were obtained. The name was revived by Goeppert[755] as a substitute for _Pissadendron_[756] adopted by Endlicher and Unger: Scott[757] employed the older name in the account of his investigations, which have added greatly to our knowledge of Witham’s types. The distinguishing characters of _Pitys_ are: the Araucarian pitting of the secondary xylem, the large pith, the occurrence of numerous small primary xylem strands of mesarch structure in the peripheral region of the pith, and the simple nature of the leaf-traces. Nothing is known of the extrastelar tissues, and beyond the fact that the species were arborescent we have no information with regard to the foliar[758] or reproductive organs. [Illustration: Fig. 486. _Pitys antiqua._ Central region of stem, showing primary xylem strands as black dots. (Kidston Collection, 598 A.)] _Pitys antiqua_ Witham. In 1899 Scott[759] published a preliminary description of some sections in the possession of Dr Kidston from Lennel Braes (Berwickshire: Calciferous series) under the name _Araucarioxylon antiquum_, but in the more complete account the name _Pitys_[760] is adopted. The following description is based on Scott’s paper and on the examination of the sections. Fig. 486 represents a diagrammatic sketch of a section (2·7 × 2·7 cm.) of the central region of a stem which had lost most of its secondary wood. In some cases the pith reaches a diameter of 3 cm.; it consists of large parenchymatous cells broader than deep, several of which contain a black substance and are probably secretory elements: the intercellular spaces are fairly large. Horizontally extended gaps, due to shrinkage and collapse, occur in the pith and give to it an appearance not unlike that of _Cordaites_. Numerous small elliptical strands of primary xylem, 0·15–0·3 mm. in diameter, are scattered in the peripheral region (fig. 486) at varying distances from the inner edge of the secondary wood and occasionally, when about to bend outwards as a leaf-trace, a primary xylem-strand abuts directly on the secondary xylem. The protoxylem occupies a more or less central position in each mesarch strand (fig. 487, B, _px_): the centrifugal tracheids have the Araucarian pitting while the centripetal elements are spiral. A few parenchymatous cells are associated with the more central tracheids. A leaf-trace about to bend outwards into the zone of secondary wood is double, but at a slightly higher level in its course it assumes the form of a single strand. The foliar bundles are thus single and not true double traces. Scott recognised, at the extreme edge of the pith, an association with outgoing leaf-traces of a single