Obscure as are the animal remains of these old Lingula-flags, the traces of vegetation are yet more difficult to make out and to describe. Easier, too, are they to describe than to figure; for, mere shallow impressions and stains as they are upon the cleaved rock, it is easier to see their remote resemblances to some known forms than to convey an idea of them by the finest lines that the graver will cut upon the wood. And then how unsatisfactory to spend days in elaborating the representation of a mere fragment, the very characters of which we are in doubt about.

We shall shortly present our readers, however, with figures of the most illustrative specimens we can obtain of those sea-weeds of the primeval shores, the Cruziana semiplicata, the Chondrites (?) acutangulus, and Chondrites (?) informis.

During a visit to the Giant's Causeway in the month of September, 1857, I made a few notes and sketches on the spot, having reference more particularly to the determinating of the stratigraphical position of the Causeway itself, and to get if possible a clear idea of the structure of the exposed cliff-sections of the basalts in the immediate neighbourhood. On comparing my observations with an account of the causeway and the adjoining coast given by the Rev. John Dubourdien in his statistical survey of the county of Antrim in 1812, I was struck with the discrepancies which exist between them, the author's idea being that the bed of Basalt forming the Causeway extended eastward to Portmoon, a distance of two-miles (page 46), and that the whole of the strata are parallel to each other. These suppositions are, as far as I am aware of, adopted by all subsequent writers on the Causeway; and as they are errors, a transcript of my notes may not be unacceptable to the readers of the “Geologist;” they tend at least to illustrate more fully the structure of the Basaltic deposits to which I allude, and are a few additional facts added to our present information on this interesting subject.

The shells of which this genus is composed differ much in their external shape and appearance, hence the great difficulty of correctly determining the limits of certain species. The character of this extinct genus are now so well understood that it is scarcely necessary to make any further allusion to the subject; but we may briefly repeat, for the sake of the less initiated, and in order to shorten the descriptions of the various species, that all possess a straight hinge-line, and a triangular or sub-parallel area, which is divided by a triangular fissure, this last being more or less covered, or contracted, by the means of one or two curved plates, to which the term pseudo-deltidium has been applied. The pseudo-deltidium is rarely preserved in the carboniferous specimens, but did certainly exist in the perfect or living individuals. The valves are articulated by the means of curved teeth developed on either side of the fissure in the ventral valve, and which fit into corresponding sockets in the opposite or dorsal one. In the larger valve the teeth are supported by vertical plates of greater or lesser dimensions, and in the space between these on the bottom of the shell are situated the muscular impressions. The adductor, or occlusor muscle leaves a narrow mesial oval-shaped scar, and on either side are situated the cardinal, or divaricator muscular impressions. In the interior of the smaller, or dorsal valve there exists two large conical spiral coils, which nearly fill the interior of the shell, the ends being directed outwardly towards the cardinal angles, while the bases of the hollow conical spires nearly meet at the hinge side, but are wide apart in front.