Cardiocarpon acutum

The species now represented, occurs, occasionally in the shale, and always, or, at least, most commonly, in groupes; as is the case in the present instance. This circumstance makes it probable that they were clustered together when they were growing on the plant and that they were either deposited where they grew or that they had been drifted but a short distance. Each grain is lenticular always acute at one end and sometimes so at the other, but more generally obtuse. The acute end (d) appears to have been the apex and the obtuse end the base. The face of the grains exhibits two distinct appearances. In some there is a slightly elevated line running through the axis from base to apex and a little scar placed at the very base across the elevated line which is perpendicular to it and which seems to rise out of it. Others have, distinctly, a circle (c) within the margin the axis of which is traversed by a line (b) which at its upper end has the distinct remains of a small double scar (a.) The former appear to be grains seen from the outside; the latter from the inside Such being the structure of these grains as far as they retain any decided characters we are justified in coming to the following conclusions about them. They probably grew in heads or dense clusters of some kind. They were didymous that is to say they grew in pairs applied by their faces c being the line of their commissure, b the impression of their woody axis and a the scars caused by the passage of the vessels of the axis into each grain. They were not adherent to the calyx for it is to be presumed that the little scar described as existing upon the outside at the base of the grains indicates the former presence of a calyx at that place.