We have no definite information as to the plants which bore _Pachytesta_, but it is probable that they were members of the Medulloseae. Grand’Eury[875] believes _Pachytesta_ to be the seed of _Alethopteris Grandini_, though this view requires confirmation. This author figures several _Pachytesta_ seeds attached in two oblique rows to a comparatively slender axis which may be the rachis of a large compound frond[876]. Renault and Zeiller[877] have figured specimens of _P. gigantea_ and _P. incrassata_ from Commentry which afford a good idea of the form of these large seeds; the genus is recorded also from Gard, Blanzy[878], and other localities. Kidston[879] described a large oval seed, blunt at each end, from the Middle Coal Measures of Lancashire as _Carpolithus Wildii_ which he thinks may be allied to _Pachytesta_, but adds, ‘I do not think we are justified in placing mere impressions of plants in genera, whose distinctive characters are derived from their internal organisation, unless there is conclusive evidence to show their identity.’ On this specimen Arber[880] has founded a new genus _Megalospermum_, but as the type-specimen shows no distinctive features other than large dimensions it would seem preferable to retain the more general designation _Carpolithus_[881]. Another example of a seed that may be generically identical with _Pachytesta_ is that described by Lesquereux from North American Coal Measures as _Rhabdocarpus Mansfieldi_ and more recently recorded by White from Missouri as _Rhabdocarpus (Pachytesta) Mansfieldi_[882]. There is little doubt that this and other species of seeds preserved as impressions are examples of _Pachytesta_ but, as Kidston says, it is preferable to reserve the name for specimens showing anatomical features. =Stephanospermum.= Brongniart. The genus _Stephanospermum_, founded by Brongniart[883] on petrified specimens from French Stephanian beds, affords a good example of a radiospermic seed without ribs differing in certain well-marked characters from such seeds as _Lagenostoma_, _Physostoma_, and _Conostoma_, notably in the complete separation of the nucellus from the integument and in the possession of a nucellar vascular system. The descriptions by Brongniart and Renault[884] have been extended by the thorough investigations of Oliver[885]. _Stephanospermum akenioides_ Brongniart.