III. On the structure and affinities of fossil plants from the palæozoic rocks.— II. On spencerites, a new genus of lycopodiaceous cones from the coal measures, founded on the lepidodendron spenceri of Williamson

The fossils which form the subject of the present paper are Cryptogamic strobili showing evident Lycopodiaceous affinities, but differing in important points from other fructifications of that family, so that it appears necessary to establish a new genus for their reception. The specimens are derived from the Coal-measures of Lancashire and Yorkshire, and are calcified, the internal structure being thus preserved in considerable perfection. As our present knowledge of the forms in question is entirely due to the researches of the late Professor W. C. Williamson, it will be necessary to give a short historical summary of the results which he attained, before going on to my own observations.