A New and interesting species of Trilobite having lately been obtained by Professor A. Liversidge, F.C.S., F.G.S., of the University of Sydney, in the Silurian rocks of Bombala, New South Wales, and forwarded to my colleague, Mr. R. Etheridge, jun., F.G.S., with a series of other Palæozoic fossils, from Australia, it has been obligingly placed in my hands for description.

Nearly every text-book on geology speaks of the heat which has been lost by the earth, and the consequent contractions which have taken place upon its surface. The way in which all this has come about, however, is either not explained at all or else very imperfectly, and the difficulty experienced by any one endeavouring to find out what the conditions have been will be fully recognized by reference to the lengthy correspondence which was carried on in the columns of Nature (December, 1878, and January, 1879) between Mr. A. R. Wallace, Mr. O. Fisher, and others, upon this subject.

A Portion of the district referred to in this paper was described by me in a communication to the Geological Society, on May 22nd, 1878, and this was afterwards published in the Quart. Journ. Geol. Soc. vol. xxxiv. In that paper, however, many of the facts which had led me to the conclusions stated therein had to be omitted, and the important evidence derived from the microscopical examination of the rocks was hardly touched upon. It was then intended that this evidence should be given in an appendix to the paper, but, unfortunately, circumstances at the time prevented it.

The study of the Palæozoic Tubicolar Annelides has not received that amount of attention which the importance of the Order, either from a geological or zoological point of view, appears to demand. True it is that many interesting and instructive papers and memoirs have from time to time appeared, containing descriptions of species, and occasionally of genera; but, so far as I know, at any rate in this country, no connected account of either Silurian, Devonian, or Carboniferous Tubicolar Annelida has appeared.

Various investigations of the Perlitic structure in igneous rocks have resulted in its being regarded as a product of unequal contraction in a cooling mass of lava. Professor Bonney, in a paper on Columnar, Fissile, and Spheroidal Structure, has compared it to the roughly-concentric joints to which, in certain basalts, the spheroidal character is due; and Mr. S. Allport, in his account of certain Ancient Devitrified Pitchstones and Perlites, writes that “an examination of all the facts leads to the conclusion that the perlitic texture is purely a phenomenon of contraction.” Of this, then, there has practically been no doubt; but, so far as I am aware, the structure has not until recently been imitated by artificial means.

1. The granitoid (Dimetian) rocks of Anglesey pass down into an anticlinal of dark gneiss (above) and grey gneiss (below). The gneiss is also seen in the Menai anticlinal.

2. Low down in the granitoid series are bands of felsite, hälleflinta, and felspathic breccia, which can lay no claim to the rank of a distinct group (Arvonian).

3. The schistose series at Ty Croes is brought into contact with the principal quartz-felsite and hälleflinta band by a fault, and there is, therefore, no proof, from this section, that the schists are of Pebidian age.

Some repetition may be avoided in this note by roughly grouping the specimens, which have been forwarded to me by Dr. Callaway, as (A) Felsitic Rocks, or those resembling felstones; (B) Granitoid and Gneissic Rocks; and (C) Dioritic Rocks. The numbers attached correspond with the reference-numbers in Dr. Callaway's paper. I may mention that in examining the slides I was ignorant of their bearing on the views propounded by the author, and, in some cases, of the exact locality of the specimens.

In Mr. Clement Reid's paper, “The Glacial Deposits of Cromer,” Geol. Mag. Feb. 1880, at p. 56, the bracket for ‘Lower Glacial’ should not include the ‘Forest Bed.’