Interruptions in the continuity of a Coal-seam, whether in the form of intercalated layers of sand or shoals of clay, are not rare; but I have been able to find little on record concerning the occurrence of pebbles of any considerable size, except where there was reason to suppose that the miners had struck upon an old river channel. The Boulder, which forms the subject of this paper, was found in the 13th Coal of the sinkings belonging to the Cannock and Rugeley Colliery Company; and I am indebted to the kindness of its manager, E. C. Peake, Esq., for the opportunity of exhibiting the specimen and for much of the following information. The seam occurs at a depth of about 540 feet from the surface of the ground; the Boulder was completely enveloped in the coal, but its precise distance from the top of the seam was not ascertained. This 13th coal is considered to be identical with the 12th coal in the Brereton Colliery. In the latter colliery this seam is about 135 feet above the lowest or 15th coal; and by boring to a depth of 68 feet, red rocks were reached, which very probably, like those detected in the sinkings at Halesowen, belong to the passage-beds between the Silurian and Old Red Sandstone.

The article by Mr. Clifton Ward upon “Rock Fissures” in the GeologicalMagazine for June, has reminded me of a special characteristic of some igneous rocks, which has been perhaps as yet imperfectly appreciated. I mean by igneous rocks, such masses of subterranean, mineral matter as have apparently thrust themselves upwards to the surface of the globe by a process of internal expansion or intumescence, caused by heat —not always attaining absolute fusion, but in some degree owing to the general permeation of the matter by super-heated water, or steam, or other gases.

The genus Conularia was first described by Miller about the year 1820, and afterwards more fully by Sowerby, as a “conical hollow univalve shell,” (Min. Con., vol. iii. p. 107). It had previously been figured by Ure under the name of a “curious fossil” (History of Rutherglen and E. Kilbride, p. 330). Sowerby, amongst other characters, noticed that in one of his specimens, formerly in Miller's collection, the edges or “lips” of the broader or truncated end of the shell were inflected, and nearly met in the centre (l. c. t. 260, fig. 4).

The Lamellibranchiata of the Scotch Carboniferous beds appear to agree on the whole tolerably well with those of the series as developed further south, notwithstanding we here and there meet with well-marked varieties, and occasionally new species. These are not so numerous as might have been expected when we take into consideration the very different physical conditions which must have existed during the deposition of the series in the two areas.

Crystallographic, like all other formulæ, are simply short-hand methods of describing that which could otherwise only be rendered intelligible by the expenditure of many words, and, in type, by considerable waste of space. Anything, therefore, which tends to simplify and contract formulæ, without diminishing the amount of information which they convey, must necessarily be advantageous. The different systems of notation used at the present time by eminent crystallographers render the comprehension, of their formulæ somewhat difficult to the student; and it would doubtless be productive of much satisfaction if a universal system of crystallographic notation could be adopted.

After reading the review of Prof. Wyville Thomson's “Depths of the Sea,” in the May Number of the Geol. Mag., in which, a figure and short description are given of a new living Echinoderm, which Prof. Thomson has named Calveria hystrix, one of whose peculiar features lies in its possessing overlapping plates, it may be interesting to readers of the Magazine to know that besides the other species with overlapping plates noticed in the above-mentioned review, there were Echinoderms having their plates arranged on the same plan as long ago as the Lower Carboniferous Limestone period. Those to which I specially refer belong to the genus Archœocidaris.

East Cumberland.—In the Cross Fell and Alston Moor district the Mountain Limestone is split up into numerous beds of limestone, sandstone, and shale, the thickness and character of which are well known through the local names given to each horizon by the miner, and from the writings of Messrs. Westgarth Forster, Sopwith, and Wallace.