_Archaeopitys Eastmanii_ Scott and Jeffrey. The genus _Archaeopitys_[770] has recently been instituted for a specimen of a stem from the Lower Carboniferous rocks of Kentucky which differs from _Pitys antiqua_, the type with which it is most closely allied, in the position and behaviour of the primary vascular strands in the pith. The type-specimen is a piece of stem 2·7 cm. in diameter including a solid parenchymatous pith 5·5 mm. broad and a cylinder of secondary wood. The wood is similar to that of _Cordaites_; the tracheids have 2–3 rows of pits but for the most part the details of structure are not preserved; the medullary rays are both uniseriate and multiseriate and not very deep; the structure is more Cordaitean than Cycadean. A characteristic feature is the occurrence of about 30 vascular bundles in the medullary region: these mesarch strands, with the protoxylem near the centre, are scattered through the pith and several lie on the outer edge in contact with the secondary xylem or are partially embedded in the xylem-cylinder. The examination of a series of sections demonstrated the fusion of perimedullary with medullary strands and the occasional union of the strands of both regions with one another. It appears that the perimedullary strands are the leaf-traces while the strands deeper in the pith are merely branches from the peripheral leaf-trace strands. In _Pitys antiqua_ the medullary xylem strands are confined to the outer zone of the pith and constitute the leaf-traces: in _Archaeopitys_, on the other hand, the medullary strands are scattered through the pith and the leaf-traces are restricted to the circummedullary region in actual contact with the secondary xylem. In the Devonian genus _Callixylon_ there are similar strands but they are confined to the edge of the pith and are usually in contact with the wood as are the circummedullary strands in _Archaeopitys_. The grouping of the secondary xylem of _Callixylon_ into wedge-shaped masses at the inner edge of the cylinder is a characteristic feature; this feature is less definite in _Archaeopitys_ and absent from _Pitys_. =Callixylon.= Zalessky.