Little is known of the Upper Jurassic Fish-fauna from discoveries in British Formations; and though considerable information upon the subject has already been acquired, this has been chiefly obtained from the fine Lithographic Stones of Bavaria, Würtemberg, and France. In these deposits, as is well known, fishskeletons are found in an almost complete state, with the bones remarkably well preserved; and the only obstacle to the satisfactory determination of the various elements is the extreme compression to which the fossils have been subjected and the hardness of the matrix in which they are enveloped.

At the last meeting of the British Association the writer briefly described a remarkable series of bones of a large unknown fish from the Oxford Clay of Peterborough, preserved in the collection of Mr. Alfred N. Leeds, of Eyebury. The name of Leedsichthys problematicus was proposed for the genus and species thus indicated; and the systematic position of the fish remained doubtful, owing to the fragmentary character of its skeleton.

Astay in Finland of some months' duration (in the summer of 1885) enabled me to make an acquaintance of considerable intimacy with the Archæan rocks of that very interesting district.

Echinarachnius Woodi was founded by Forbes in his “Monograph of the Echinodermata of the British Tertiaries” on two fragments from the Red Crag of Suffolk; of all the species described in that work, this has been regarded as the most interesting and problematical. As this species certainly belonged to a genus now foreign to the British or European seas, it was felt, that if its correct generic position could be determined, it and Temnechinus would indicate the true affinities of the Crag Echinoderm fauna, better than the cosmopolitan genera with which they were associated.

I Have derived much help towards understanding Mr. Harker's instructive letter upon the above subject from making the following simple geometrical construction.

Fossil Mammalian remains from Olivola were already known in the last century. Giovanni Targioni Tozzetti describes and figures several bones from that locality, which he refers to some species of Tricliechus or Phoca, but which, as far as the figures permit of a judgment, belonged to Ruminants. In this century, the deposit was mentioned by Pareto, and by Cocchi, who from stratigraphical considerations ascribe it to the Pleistocene.

As Dr. Callaway has asked in a recent Number of the Geological Magazine for the grounds on which I suggest that some of the volcanic rocks of Shropshire may perhaps be classed as Cambrian, I take this opportunity for bringing before your readers the present state of the inquiry into the nature and classification of the earliest sedimentary rocks in this country. This inquiry has been spoken of by Dr. Callaway as the “Archæan controversy”; but we must not necessarily call everything that is earlier than the Cambrian “Archasan,” any more than in old days it was right to call everything Precarboniferous “unfossiliferous greywacké”; nor should the inquiry be considered a controversy in its present stage, but rather a search for more accurate knowledge.

In the deposits previously described what takes place appears to be about as follows. The larger flakes of biotite undergo an alteration which largely produces epidote, and not improbably granular rutile, though this is not at all proved. Crystals of rutile very rarely result during the process. Such of the iron of the biotite as is not combined in the epidote (which is strongly coloured) is removed in solution, some of it being deposited again as limonite diffused throughout the deposit, and some taking part in the formation of the thin bands of ironstone, being precipitated as carbonate.