g6 Scott and Maslen . — The Structure of Trigonocarpus. 
tissues of the petiole of Medullosa anglica 1 as further evidence of the 
probable relationship of Medullosa and Trigonocarpus. As we shall show 
later on in this paper, the similarity is possibly not quite as close as Wild 
supposed. 
The principal object of the present paper is to present the results of 
a detailed examination of a large number of sections of the common form 
of Trigonocarpus (T. Parkinsoni). Many of the sections and specimens are 
in Dr. Scott’s collection, and others have been borrowed from various 
sources including the British Museum (Natural History), the Manchester 
Museum, the Newcastle Museum, the Cambridge University Collection, 
and that at University College, London. For facilities to examine these 
and other specimens we are indebted to Mr. E. A. Newell Arber, F.G.S., 
Mr. W. E. Hoyle, D.Sc., Prof. F. W. Oliver, F.R.S., Prof. M. C. Potter, 
F.L.S., Prof. A. C. Seward, F.R.S., and Dr. A. S. Woodward, F.R.S. 
After describing the common form we shall briefly describe a new 
species obtained from a roof-nodule at Shore-Littleborough, Lancashire. 
The slides have been submitted to us for examination by Prof. F. W. Oliver, 
F.R.S. , after whom we have named it Trigonocarpus Oliveri . A short 
account will then be given of some features of interest in connexion with 
the casts and impressions, and finally a second part of the paper will be 
devoted to a discussion of the general bearing of our work and the probable 
affinities of the seed. 
III. Trigonocarpus Parkinsoni, Brongn. 
General characters of the seed. 
The seed as ordinarily preserved in the petrified condition is large, 
and of an oval form which is well shown in the longitudinal sections figured 
by Hooker and Binney 2 and by Williamson 3 . The general oval shape of 
the body of this seed as seen in the longitudinal sections is very character- 
istic, and different from that of the new species Trigonocarpus Oliveri 
(PI. XIII, Fig. 19). The greatest width is about half-way up the body of 
the seed, i. e. of the rounded part excluding the micropylar beak. The 
transverse sections across the body of the seed show the three prominent 
ridges on which the generic name is based (see PI. XI, Fig. 5). There is 
but little variation in size among the seeds which we have examined, and all 
appear to be in about the same stage of development. Some of the largest 
specimens which we have examined have a maximum diameter across the 
body of the seed (measuring to the outer margin of the hard testa only) of 
about 1-6 cm. The usual transverse diameter is less than this, about 1*3- 
i* 4 cm. The length of the body of the seed, without the micropylar beak, 
is usually 3-3*5 cm> 
1 Scott (’99). 
2 Hooker and Binney (’55). 
3 Williamson (77). 
