Heer[1033] proposed this generic name for some globose, ovate, or oblong ‘fruits’ from Lower Carboniferous strata in Spitzbergen, including also fragments of ‘leaves’ which without satisfactory evidence he believed to belong to the same plant. The supposed fruits are clearly seeds, and Nathorst regards the ‘leaves’ as portions of a Fern rachis. Heer described four species, but these have since been reduced to two, and indeed it is probable that only one type, _Rhynchogonium costatum_, is represented. Nathorst[1034] compares Heer’s seeds with a Lower Carboniferous species described by Young[1035] as _Trigonocarpum gloagianum_, the resemblance of which to the Spitzbergen seeds was pointed out by Kidston. A seed of _Rhynchogonium costatum_ is about the size of a hazel-nut and may reach a length of 21 mm.; it is ovate, with a broad rounded base, and in the upper third is tapered and conical, the sides of the characteristic snout being distinguished from the smooth surface of the rest of the seed by the presence of eight ribs converging towards the apex (506, G). Zalessky[1036] recorded closely allied seeds from Lower Carboniferous beds in Northern Russia, assigning them to a new genus _Boroviczia_, the type-species being _B. Karpinskii_; he adduced arguments in favour of Heer’s interpretation of the fossils as fruits but, according to Nathorst, this view has been abandoned. In his recent memoir on the Culm flora of Spitzbergen Nathorst[1037] discusses the morphological nature of _Rhynchogonium_ seeds and describes additional specimens. Without the aid of petrified examples it is hardly possible to determine the true nature of the fossils. [Illustration: Fig. 506. A, _Holcospermum sulcatum_. B, C, _Codonospermum anomalum_. D, _Diplopterotesta spitzbergensis_ (× 3). E, _Gnetopsis elliptica_ (cupule). F, _Thysanotesta sagittula_. G, _Rhynchogonium costatum_. H, _Hexagonocarpus Noeggerathi_. I, _Boroviczia Karpinskii_. K, _Rhabdospermum tunicatum_. (A, Kidston Collection; B, after Grand’Eury; C, after Renault and Zeiller; D, F, G, after Nathorst; E, after Renault; H, after Williamson; I, after Zalessky; K, after Berger.)] Some specimens of _Rhynchogonium sulcatum_ in Dr Kidston’s collection show the original surface-features: the carbonised integument is divided in the upper region into linear lobes separated from one another at their origin by fairly wide sinuses, a type of integument suggesting comparison with _Physostoma_. This species was originally described by Lindley and Hutton as _Carpolithes sulcata[1038]_ from Lower Carboniferous rocks at Newhaven in Scotland and has recently been figured by Zalessky[1039] from specimens in the Kidston collection from the Lower Calciferous sandstone of Midlothian. Nothing definite can be said as to the parent-plant, but it is significant that in Midlothian _Rhynchogonium sulcatum_ occurs in a bed full of isolated pinnules of a _Cardiopteris_ almost to the exclusion of any other fossils[1040].