that is specifically identical with _T. Parkinsoni_ Brongn. This author also drew attention to the close resemblance between Brongniart’s three genera _Trigonocarpus_, _Hexapterospermum_, _Tripterospermum_ and expressed doubts as to the possibility of founding specific differences on casts of the _Trigonocarpus_ type without the evidence of anatomy. Our knowledge of the structure of _Trigonocarpus_ has in recent years been considerably extended by the researches of Oliver, Scott and Maslen, and Salisbury. [Illustration: Fig. 423. Casts of the seed-cavity of _Trigonocarpus Parkinsoni_. (Manchester Museum. ½ nat. size.)] _Trigonocarpus Parkinsoni_[337] Brongniart. The seeds of this species like all examples of the genus are radiospermic, that is radially symmetrical in contrast to the flattened or platyspermic seeds. The complete seed is elongate oval in form when preserved as an impression (fig. 425, A) and reaches a length of 4–5 cm.: the casts of the seed-cavity are ovoid and provided with three prominent ridges (fig. 424, 2, 3). The testa forms a thick covering differentiated into three regions, an outer flesh or sarcotesta, a sclerous shell or sclerotesta, and an inner flesh. Transverse sections show that the sclerotesta has three sharp longitudinal keels with corresponding furrows on the inner face, and between each pair of main ribs are 2–3 less prominent ridges, usually 12 in all (fig. 426). The sarcotesta consists of thin-walled parenchyma passing externally into a more lacunar tissue with a palisade-like hypoderm: the sclerotesta consists of thick cells which interlace and form an efficient protective shell. Both the sarcotesta and sclerotesta are continued into the apical region as the wall of the long micropyle, the sarcotesta being prolonged beyond the sclerotesta at the apex of the integument[338]. The micropyle is triangular in section and may exceed in length the whole seed (figs. 425; 426, A). Its form as seen in transverse section (fig. 426, B) suggests the presence of wings: this appearance may be deceptive and due to pressure or, more probably, it represents an original feature. The seed-body, that is the portion enclosed by the integument, consists of the nucellus, represented by a few crushed layers of cells, bounded by a well-defined epidermis; the nucellus is separated from the integument from the base of the seed upwards, an important feature in which this and some other Palaeozoic seeds differ from _Lagenostoma_ and the seeds of recent Cycads which are characterised by an integument adnate to the nucellus up to the level of the shoulder; the seeds of the Conifer _Phyllocladus_ afford an example of separation of integument and nucellus as in _Trigonocarpus_. The innermost layer of the nucellus consists mainly of tracheal tissue investing the large megaspore (fig. 426, A, C, _m_) which is preserved as a contracted membrane detached from the nucellus after the death of the seed. At the summit of the nucellus is