This species is represented by ellipsoidal seeds, 10 mm. long with a maximum breadth of 4–4·5 mm., circular in transverse section. The integument consists of a thick sclerotesta lined internally by a thinner soft layer, the endotesta (fig. 494, A, _sc_, _e_), and in all probability covered by an outer flesh or sarcotesta as in _Trigonocarpus_, though this tissue is not preserved and is omitted from the section shown in fig. 494, A. The sclerotesta is composed of a broad outer band of thick-walled palisade cells—the contracted contents of which are a striking feature in the silicified seeds (fig. 493, F); these are succeeded by an inner zone of longitudinal fibres. In the structure of the palisade-layer _Stephanospermum_ bears a close resemblance to the sporocarp wall of _Pilularia_[886]. In the apical region the shell forms a circular ridge surrounding a peri-micropylar trough, a character expressed by the term ‘crown-seed[887]’ employed by Grand’Eury: the trough sometimes contains partially destroyed tissue that may be a remnant of a sarcotesta. A _Stephanospermum_ seed, with its apical core and surrounding depression with remnants of some partially destroyed tissue, may be compared with a fruit of _Attolia speciosa_ (Palmae) in which a tuft of fibrous tissue picked out by decay from the mesocarp surmounts the conically pointed apex of the harder interior of the fruit-wall. The base of the sclerotesta is perforated by a vascular strand which expands into a tracheal disc, _td_, fig. 494, A, at the base of the megaspore from which a continuous mantle 2–3 cells broad, of short spiral and scalariform tracheids (fig. 493, G), spreads over the whole of the nucellus immediately below the nucellar epidermis as far as the lower part of the sides of the pollen-chamber: this mantle forms the floor of the large domical pollen-chamber excavated out of the nucellar cone (fig. 494, A, _pc_). The fact that in sections of older seeds the tracheal floor shows signs of splitting and disorganisation led Oliver to conclude that in the living seed the tracheids underwent a gradual disintegration prior to fertilisation, thus allowing the passage of the antherozoids to the egg-cells (fig. 494, A, _a_). The presence of a continuous tracheal sheath instead of separate vascular bundles is a special feature in which _Stephanospermum_ differs from _Trigonocarpus_ and other Palaeozoic seeds as well as from those of recent Cycads; as Oliver suggests, ‘the apparent perfection of the vascular mantle in _Stephanospermum_ may have proved an obstacle to further development[888]’ and was not retained by the more successful types. In its tracheal sheath _Stephanospermum_ resembles the seeds of _Ginkgo_. The nucellar cone is prolonged as a beak into the micropyle formed by the tubular integument. The megaspore occupies the central portion of the seed and in the course of its development it compressed the megasporangium (nucellus) to such an extent that little more than the