Among the metamorphic phenomena which seem to me deserving of more attention than they have yet received, I have been especially interested by those existing in the brecciate formations. They are, of course, in the main, two-fold; namely, the changes of fragmentary or rolled-pebble deposits into solid rocks, and of solid rocks, vice versa, into brecciate or gravel-like conditions. It is certainly difficult, in some cases, to discern by which of these processes a given breccia has been produced; and it is difficult, in many cases, to explain how certain conditions ofbreccia can have been produced either way. Even the pudding-stones of simplest aspect (as the common Molasse-nagelfluhe ofnorth Switzerland) present most singular conditions of cleavage and secretion, under metamorphic action; the more altered transitional breccias, such as those of Valorsine, conceal their modes of change in a deep obscurity: but the greatest mystery of all attaches to the alterations of massive limestone which have produced the brecciated, or apparently brecciated, marbles: and to the parallel changes, on a smaller scale, exhibited by brecciated agate and flint.

Since the occurrence of Chitons, in the Mountain Limestone of Settle, was noticed by one of us, in 1862, other remains have been found in the same rock, as well as in the Carboniferous Limestone and shales of Scotland. The former were discovered, as before, by Mr. J. H. Burrow, of Settle, who has kindly placed them in our hands for description.

I came accidently upon the deposits which are the subject of this brief notice, the afternoon before I Left Llandudno last April. Want of time prevented my making more than a hasty examination of them, but I think that they will repay any one who happens to be visiting Llandudno this summer, and will devote a day or two to them.

A recent visit to the picturesque lake-valley of Glen-car, about seven miles N.N.E. of Sligo, has afforded an opportunity for reconsidering the method by which the fine precipices enclosing it were formed.

The Rocks included under this head are those already described by Professor Phillips, in his paper “On Group of Slate Rocks in Yorkshire, between the rivers Lune and Wharfe, etc.” (Trans. Geol. Soc., 2nd Series, III. 1). Also by Professor Sedgwick, in his paper “On the Lower Palæozoic Rocks at the base of the Carboniferous Chain, between Ravenstonedale and Ribblesdale” (Quart. Journ. Geol. Soc. VIII. p. 35).