TRIGONOCARPON, a common fruit in the coal-measures, occurring in all the strata except the underclays and limestones. Some six or eight species have been established, which differ from each other in size and shape—some being as small as a pea, and others as large as a walnut. They are marked, when preserved in the round, with three longitudinal ridges, and from this character the name was derived. They have never been found attached to any plant. From their shape, and their occurring in such quantities in some localities that they might be gathered by the bushel, it was at first thought that they were palm-fruits; but Dr. Hooker, from the examination of several specimens which exhibit structure, has shown that they are not unlike the structure of salisburia, a drupe-bearing coniferous tree, a native of China and Japan. He found that they were composed of four distinct integuments, and a large internal cavity tilled with carbonate of lime, but which, he supposed, originally contained the albumen and embryo. The determination of the affinities of this fruit is the more important, as the
existence of conifers in the coal-measures was known from the occurrence in them of disk-bearing wood* tissues; and the absence of linear leaves and cones makes it the more likely that they belonged to the drupe-bearing division of the order. It is proba ble that the trunk, to which the generic name dadoxylon has been given, and the casts of the large pith of which is known as sternbergia, had for its leaves the fern-like fossils named noggerathia Ilabellata, and trigonocarpon for its fruit. Dr. Dawson has, however, recently referred some trigonocarpa to sigillaria, and he considers the anomalous organ ism called antholites to be the bud-form of the fruit. He has never found them in con tact with sigillaria, and it is much more probable that this was a cryptogamous tree, and consequently had spores, and not seeds, for its fruit.