In 1865 my friend Mr. Edward Wunsch, of Glasgow, made the discovery of some thin carboniferous shales imbedded in volcanic ash at Laggan Bay, in Arran. These beds have already been described by their discoverer, and their fossil contents referred to by Mr. Binney, Mr. Carruthers, and Sir Charles Lyell. From within a very limited area the bases of more than 13 large erect stems of carboniferous trees have been extracted by Mr. Wunsch, the most important of which he has kindly placed in my hands. In the summer of 1877 we conjointly superintended some quarrymen, who tore up large portions of these strata with the result, I believe, of obtaining a fair knowledge of the nature of these beds and their contents. The trees certainly stood where they originally grew; most of them consisted of a thin cylinder of the outer bark, which was deeply
fissured
longitudinally but exhibited no true Sigillarian flutings or traces of leaf-scars. The interior was in most cases filled with volcanic ash, but in a few instances by vegetable débris introduced from without; and in one specimen, imbedded in the vegetable mass, are several decorticated Diploxyloid vascular axes of very old stems. These have been referred to as young growths that sprang up within the bark-cylinder; but such is not the case. Each one is not only decorticated, but is large enough to be the vascular axis of the large tree within which the entire group occurs, and where they are mixed up with fragments of the similar vascular axes of
Stigmaria
and other plants.
Shakedown of a Thick Cylinder With a Radial Crosshole