The Lake District differs from other parts of England in the comparative absence of table-lands or broad upland plateaux. The original mountain-masses have in most parts been eaten into by denudation to such a depth as to leave only a series of narrow ridges or edges which act as buttresses to small peaks. When the pedestrian has climbed up from the inner end of one profound excavation, he finds himself on the brink of another. The larger valleys are deepest at their inner ends, and shallow out and narrow off towards their entrances. Their floors fall so slightly outwards that were the outlet stream-channels to be filled up, the valleys would be converted into troughs. In most instances their mouths are confronted by higher ground, and this is sometimes so strikingly the case that in approaching a valley from the surrounding belt of Carboniferous strata, you find yourself going down instead of up among the mountains. The highest ground is not in the centre, but irregularly surrounds a comparatively depressed area about ten miles in average diameter. Such a configuration of country could not have been the best adapted for accommodating a quantity of snow at a high level sufficient to send very large “tongues of ice” along the radiating valleys.

In his description, Brocchi does not fail to observe that this is a very variable species. It is more or less transverse or elongated, and while some specimens are entirely smooth, others present from two to four ribs near the front in both valves, and about a similar number on each of the lateral portion of the shell, but these ribs are short and do not seem to extend far in the direction of the beaks. The ventral valve is gibbous, with a well-defined fold, while in the dorsal valve the sinus is broad and deep. In Brocchi's typical form the shell is smooth, while to the more or less plicated specimens Costa has applied the specific name oi plieato-dentata, but, as was well shown by Philippi (Enum. Moll. Sicil., vol. 2, pi. xviii., fig. 5, 1844), there exists every passage in shape between the more transverse and smooth specimens to those that are more elongated and plicated near their margin. Rh. bipartita is also stated by Meneghini and others to occur in the Middle (?) and Upper Miocene, as well as in the Older Pliocene.

The Chalk from Cop-point, near Folkestone, to Walmer in Kent, has been so well described by Mr. W. Phillips, that I need do little more than allude to his paper, in reference to the divisions of the Chalk in East Kent; but in a notice of the Isle of Thanet by the Rev. W. D. Conybeare, this gentleman, from the absence of flints in the Chalk near Margate, was led erroneously to suppose it to belong to the lower division, and it was not till 1865 that this error was exposed in a paper on the Chalk of the Isle of Thanet by Mr. W. Whitaker, F.G.S., of the Geological Survey, the latter gentleman pointed out the true position of the Margate Chalk, as that of the highest Chalk, and superior to that with numerous flints seen at Ramsgate; and he there remarked, “Very likely the Broadstairs Chalk will turn out to be the upper part of the ‘Chalk with many Flints’ (Phillips) of the cliffs from Walmer Castle to Dover Castle, and which is there the highest division; so that the Isle of Thanet section would be the upward continuation of that given by Mr. Phillips.”

Since I first saw my short notice on “Faults in Strata” in print (GeologicalMagazine, 1869, Vol. VI., p. 341), I have been anxious to remove a blemish of apparent flippancy in alluding to systems as applied to faults. I had indeed in view cases where that method had been used imitatively—with the tacit assumption of an established and well-understood meaning; but I lost sight of the fact that serious special work had been devoted to the subject, and my remark was unqualified. I have to thank my friend Mr. W. T. Blanford for an opportunity of making this correction, as well as of adding some further considerations on so important a point in the principles of stratigraphy.