III.—On a Lepidodendroid Stem from the Coal-Measures

Extract

Among the numerous Lepidodendroid remains in the Geological Department of the British Museum (Nat. Hist.), there is one which presents several characters of unusual interest. It is a cast, obtained from the Middle Coal-measures of South Staffordshire, near Dudley, and belongs to the Johnson Collection.

A portion of the specimen is figured on p. 209. It will be noticed that the mammillated leaf-cushions are distant from one another, and are separated by broad bands of striated bark. This is an unusual feature in the case of British Lepidodendra. The preservation is fairly good, except in the details of the leaf-scar. In the specimen thirteen leaf-cushions are represented, forming portions of five spiral series. The cushions are rhomboidal in outline, and at first sight do not appear to be very sharply marked off from the bark. On closer inspection, however, they are seen to be moderately well defined, although the lateral angles are flattened and obscured by the encroachment of the bark. They measure from 1.8 to 2 cm. in length, and from .6 to .7 cm. at their greatest width. The upper and lower extremities lie in one plane, which is the median plane of the cushion, and are inclined neither to the right nor to the left (of. Lepidodendron serpentigerum). The cushions stand out in high relief, and depart somewhat from the form of a low truncated pyramid so commonly seen amongst Lepidodendra. However, this is in no wise remarkable, for examples of Lepidodendra having raised cushions are not rare, in cases where the stems have to some extent escaped crushing.