Scot l and Mas leu. — The Structure of T rigonocarpus. 127 
Trig 0110 car pus Oliveri differs essentially from P olylophospermum ste- 
phanense in its general shape and in the absence of the cup-shaped outgrowth 
of the testa around the micropyle. Its general shape is much less narrow 
and cylindrical, the proportion of length to breadth being about 2 : 1, while 
in P olylophospermum it is about 3:1. The shape in transverse section cannot 
be determined from our sections. 
On the whole, judging from the characters which are available in a series 
of longitudinal sections of a single seed, we think that this seed more closely 
resembles T rigonocarpus, and we have therefore provisionally placed it in 
this genus. 
The following is a brief diagnosis of the distinctive characters of the 
new seed : — 
Trigonocarpus Oliveri , sp. nova. 
Horizon . Lower Coal Measures. Shore-Littleborough, Lancashire. 
Size. Length nearly 2 cm. ; maximum transverse diameter about *9 cm. 
Shape. Characteristically J coffin-shaped ’ in vertical sections. Base 
flattened. * Sclerotesta produced around the base of the seed in the form of 
a circular ridge enclosing the stalk of the seed. Longitudinal ridges of the 
sclerotesta acute-angled, not rounded as in Trigonocarpus Parkinsoni. 
V. The Casts and Impressions. 
It is not intended in this paper to enter into a full discussion of the speci- 
mens of Trigonocarpiis which do not exhibit internal structure — the internal 
casts of the cavity of the seed and the more or less flattened specimens of the 
whole seed which have usually been described under the name of Carpolithes 
alata (Lindley and Hutton). At the same time, a correlation of the features 
shown in those specimens with those of the petrified seeds showing internal 
structure is of some interest and importance, and we propose to devote 
some attention to this matter in the present paper, especially with reference 
to the three good specimens of Carpolithes alata represented in PL XII, 
Figs. j 6 and 17, and PL XIII, Fig. 18. 
Taking first the ordinary internal casts, some account has already been 
given of these nut-like ‘ seeds ’ in the present paper (pp. 90, 94), and a few 
additional details may be given here. The common type of these internal 
casts — those described under the names of Trigonocarpus Parkinsoni and 
T. olivaeformis — although they vary somewhat among themselves in size 
and shape, still agree closely with the petrified specimens showing internal 
structure, so that it is highly probable that they represent the same form. 
The probable identity of the casts described as T. Parkinsoni and T. olivae- 
formis has already been pointed out (p. 93). 
Many of the internal casts show a triangular fracture at the narrower 
(upper) end, which doubtless represents the place where the cast of the 
