In a paper published in the Quarterly Journal of the Geological Society for 1884, I gave some account of the Tynemouth Dyke. In that paper, however, I omitted to describe one feature, connected with the microscopic structure of the dyke, because at the time of writing I did not understand it. A short time ago I had occasion to re-examine my preparations, when my attention was again directed to the feature in question; and this time an explanation suggested itself which appears to be in every respect satisfactory. The main object of this communication is to supplement my already published description by giving an account of the feature to which I have referred, and which may be briefly described as the occurrence of spherical patches of interstitial matter. (See Pl. XIV. Fig. 1.)

Those who have carefully studied the crystalline schists cannot fail to have noticed that a community of structure—a sort of family likeness—prevails throughout any one group of rocks, while those which occur apparently at different horizons exhibit dissimilar structures. Thus the marbles associated with any group of crystalline schists are coarse or fine in grain, according to the structure of the latter. But to this rule exceptions appear, at first sight, not infrequent. For instance, in the Alps, we find not uncommonly, in that group of schists which seems to occupy the highest position, marbles which present an abnormally compact aspect. On closer examination they prove indeed to be crystalline in structure, but the crystals seem so small, the general structure so compact, that until we find them graduating into typical mica or other schists, we can hardly feel satisfied we are not being duped by infolded limestones of Mesozoic or Palæozoic age.

“The study of any new science,” says Alexander v. Humboldt, “may be compared to a journey to distant lands. Before starting in company with others, the question as to the practicability of the journey is raised; while examining one's own powers, the qualities of fellow-travellers are looked upon with distrust. It is feared—perhaps without just reason—that they might cause unpleasant detention. In our time the difficulties of an undertaking of this kind are much diminished. Any confidence is founded on the bright blossoming state to which natural sciences have grown, their wealth being no more the abundant quantity, but the concatenation of what has been observed.”

In a short paper on the nomenclature of the Old Red Sandstone Fishes published in this Magazine for November, 1888, I expressed the opinion “that the scattered teeth and fragments of jaws known as Dendrodus and Lamnodus belong to fishes at present known to us by their scales as species of Holoptychius and Glyptolepis.” The family terms “Holoptychiidæ” and “Dendrodontidæ” I consider absolutely synonymous. On the other hand, the Rhizodontidæ (Gyroptychius, Tristichopterus, Rhizodus, etc.) present a somewhat different form of tooth-structure, and one which is, in the main, identical with that which, in so many Stegocephalous Amphibia, is called “labyrinthodont.”

In a recent paper on the volcanic rocks of Kilimandjaro I referred to the presence in the basaltic lavas of olivine crystals, which appeared to possess zonal structure. Although actual proof was wanting, still the symmetrical arrangement of the inclusions, as also the mode of alteration of the crystals, rendered the occurrence of such a structure highly probable. The olivines, being rich in iron, were altered into ferric oxide or ferric hydrate; and the line of division between the fresh and decomposed portions was mostly parallel to the crystallographic outlines. There was, however, no break in the optical continuity, such as the presence of zonal structure would demand.

In examining the remarkably fine series of examples of Cœlonautilus cariniferus, mostly from the Carboniferous Limestone of Ireland, contained in the Geological Collections of the British Museum (Nat. Hist.), some were found to exhibit upon the cast of the body-chamber distinct marks of the shell-muscles. In one specimen (No. 50190) these are so perfect as to give a very clear outline of their form, and some of the test having been removed, their entire course can be made out.

In the Proceedings of the Geologists' Association for 1878, Mr. W. H. Shrubsole, F.G.S., published a list of Foraminifera obtained from the London Clay of Sheppey. The following list, the result of an examination of some material courteously lent to us by Professor J. W. Judd, F.R.S., adds considerably to the fauna of Sheppey and includes two species not previously recorded from the London Clay. Forty-one forms have been determined, of which twenty-six. are new to Sheppey, thus bringing up the number of forms recorded from that locality to eighty-six. The geographical distribution of the Foraminifera of the London Clay was fully tabulated in 1886, and it is interesting to find so many of the forms there figured and recorded for the first time from the London area common to both localities. The figure following the specific name in the list appended shows the relative abundance of the varieties found.

During a visit to Stockholm last spring, Prof. Gustav Lindström kindly permitted the writer to examine the series of remains of Palöozoic fishes obtained from the Devonian of Spitzbergen by Dr. A. G. Nathorst, during the Swedish Geological Expedition in 1882. Some of the more prominent specimens have already been briefly noticed, with figures, by Prof. Ray Lankester; but the collection is worthy of a more detailed comparative study than that to which it has hitherto been subjected, and among the undescribed specimens most readily identified is a small fossil indistinguishable from the so-called “intermandibular arch” or “presymphysial bone” of Onychodus. Through the kindness of Prof. Lindström, this specimen has been forwarded to the British Museum for examination, and it forms the subject of the following remarks.