Scott and Maslen . — The Structure of T rigonocarpzis. 93 
According to Mr. Kidston 1 the earliest figured specimens of Trigono - 
carpus are those given in Parkinson’s Organic Remains 2 , published in 1811. 
These are the familiar internal nut-like casts to which Brongniart, in his 
Prodrome 3 , gave the name Trigonocarpum Parkinsoni . This name appears 
to be the earliest applied to British specimens. 
The other familiar specific name, olivaeforme , seems to have been first 
used by Lindley and Hutton for casts 4 , and afterwards by Williamson 5 for 
specimens showing internal structure. 
Lindley and Hutton figure and describe several species of Trigono- 
carpus (their Trigonocarpum ) from the casts. Some of these forms differ 
from our common form in size and shape to such an extent that we feel no 
doubt as to their being distinct species, but two somewhat similar forms 
are figured as T. Noeggerathi and T. olivaeforme. Internal casts of T. Noeg- 
gerathi are said to be provided with six longitudinal ridges instead of three 
as in T. olivaeforme. Internal casts of any of our specimens would certainly 
have only three ridges, so that T. Noeggerathi may be excluded. More- 
over, according to Mr. Kidston, T, Noeggerathi is an uncommon seed in 
Britain 6 . 
It rests, then, between T. Parkinsoni (Brongn.) and T. olivaeforme 
(L. and H.), which Mr. Kidson, after examination of the casts in the 
Natural History and other Museums has pronounced to be really indis- 
tinguishable from one another 7 . If this identification as one species is 
correct — and as far as our own observations go they are in support of it — 
T. Parkinsoni (Brongn.), as the earlier name, should be used. The common 
British specimens will therefore be described in this paper as Trigonocarpus 
Parkinsoni. 
Lindley and Hutton also figure, under the name of Carpolithes alata 8 , 
specimens which show not only the internal cast of the cavity of the body 
of the seed, but also that of the elongated micropylar canal, and an 
impression of the testa of the seed, as shown in PI. XII, Figs. 16 and 17, 
and PI. XIII, Fig. 18, of this paper. These specimens Mr. Kidston also 
identifies with Trigonocarpus Parkinsoni 9 , and we think that there is no 
doubt that they do represent a more complete form of preservation of the 
same or a similar form to that represented by the ordinary internal casts 
and the petrified specimens. 
Thus we now know the common Trigonocarpus in three conditions : — 
(1) As the common internal casts of the central cavity of the seed, 
the actual tissues having disappeared completely, or being represented only 
by a layer of structureless coal. 
1 Kidston (’86), p. 216. 2 Parkinson (’ll). 3 Brongniart (’28). 
4 Lindley and Hutton (’31-37), vol. ii, PI. 222, Figs. 1, 3. 
5 Williamson (77). 6 Kidston (’86), p. 219. 7 Kidston (’86), pp. 218, 219. 
8 Lindley and Hutton (’31— ’37), vol. ii, PI. 87. 9 Kidston (’86). 
