The genus Halonia was established in the Fossil Flora (vol. ii., p. 13) by Lindley and Hutton for those fossils in which, to the surface of Lepidodendron, is added the mode of branching of certain Coniferœ, and which were therefore inferred to be of a nature analogous to the latter. It was assumed that Lepidodendron, being an extinct form of Lycopodiaceœ, must be limited to the fossils in which the branching was dichotomous, since no other kind of branching is met with in recent Lycopodiaceœ. But when we look at such plants as Lycopodium cernuum and L. densum, we find branching precisely similar to that in Halonia gracilis, L. and H.; and whether these were produced or not by the division of a terminal bud, it is certain that in their developed condition they are arranged in an alternate manner round a common elongated axis— a plan of branching characteristic, as the authors of the Fossil Flora supposed, of Coniferœ.

In the course of last summer I visited the banks of the Dniester, in Podolia and Galizia, where I was fortunate in collecting, near Zalesczyki, a number of shields belonging to Pteraspis (Scaphaspis) Kneri, Lank.

Dr. Macalister, in his able Presidential Address, has furnished the Society with a summary of the work done, principally by German petrologists, with the object of determining the mineral constitution and structure of plutonic, metamorphic, volcanic, and other rocks, by the aid of the microscope. Forbes, Sorby, and Allport amongst ourselves have also represented British petrologists in the same field, but perhaps have not been sufficiently forward in giving the results of their labours to the world.

Having read Mr. Price's note and description of Rostellaria maxima in last month's Number (p. 97, Pl. VI.), I venture to express my regret that so doubtful a species should be published with the apparent authority of the GeologicalMagazine to confirm it; especially as Mr. Wiltshire (than whom there is no one better acquainted with English Cretaceous Mollusca) is of opinion that it is only a giant form of Rostellaria carinata. The description given by Mr. Price would equally apply to the ordinary form of R. carinata which occurs in the same bed, and, save in size, exactly resembles it. The most distinctive portion of the shell, the wing, is unfortunately not preserved. The examples of Rostellaria carinata found in this bed, I may remark, always differ slightly in form, being broader and more obtuse (they are also usually more crushed and imperfect) than those from the lower beds. I am fully; convinced that, if size alone is sufficient ground to justify the formation of new species, we shall speedily find the present confusion of names in the Gault fauna more hopelessly involved and more impossible to unravel than ever. What, for instance, would be the result of the adoption of such a basis of nomenclature for the Cephalopoda from the same formation ?

My thanks are due to Mr. Tiddeman, for his reply to the letter from me, which appeared in your February Number. I may perhaps be allowed to add a few words more upon the subjects under discussion.

A gates are found abundantly in Somersetshire. Dr. Buckland mentions their occurrence at Sandford, near Banwell, Worle, and Clevedon. Trans. Geol. Soc., ser. 2, vol. iii., p. 421, See also Sowerby's British Mineralogy, vol. v., 1817, p. 213.