Among the very few known instances of fossil hydroids, the genus Hydractinia must be included. Under the name of Cellepora echinata, M. Michelin has described a fossil from the Subapennine group of Asti, and from the Superior Fallunian of Bordeaux and Dax (Michelin, Icon. Zooph., p. 74, pl. xv., fig. 4). M. Fischer has drawn attention to the fact, that the Cellepora echinata of Michelin is really a Hydractinia encrusting a Murex or a Nassa, while he has himself added another fossil Hydractinia from the Upper Greensand of Mans (Fischer, Bull, de la Soc. Géol. de France, 2me sér. t. xxiv., p. 689). This he found in the collection of M. Alc. d’Orbigny, where it encrusted numerous specimens of Natica tuberculata, d’Orbig., from that formation. M. Fischer has assigned to this species the name of Hydractina cretacea, while to Michelin's species he has given that of Hydractina Michelini.

In the March number of the Geological Magazine, Mr. A. H. Green observes that it is difficult to account for the supply of salts to the Permian Sea. For the iron, he calls in the aid of mineral springs produced by volcanic action; but for the lime and magnesia, streams flowing into the sea holding in solution bicarbonate of lime and sulphate of magnesia.

III. Pictet converted D’Orbigny's families into tribes, and introduced some additional genera created by Giebel King, etc.; and, except in the description of new genera and species by Reuss, Roemer, Salter, Eichwald and others, the subject remained very much where D’Orbigny left it until M. de Fromentelle proposed a new arrangement, based upon what he terms the “organs which serve for the nutrition of the sponge,”—viz., the tubule, oscules, pores, etc. Like D’Orbigny, he divides the sponges into two orders: 1st, the Spongitaria, which comprises only recent genera; and, 2nd, the Spongitaria, which contains all the fossil genera, with the exception of the doubtful group, the Clionidæ. The second order is further divided into three sub-orders: 1, those sponges which have one or more tubules (the Spongitaria tubulosa); 2, those that have oscules, but no tubule (Spongitaria osculata); and 3, those that have neither tubule nor oscules (Spongitaria porosa). Each of these suborders is further divided thus: the tubular sponges into those in which the tubule is solitary, and those in which it is grouped, and also into those with oscules and those without oscules. The oscular sponges are similarly subdivided, according to form, disposition of the oscules, and presence or absence of an epitheca. Lastly, the porous sponges are divided into those that are more or less regularly cup-shaped, and those that assume some other form.

In a republication of the papers by him which appeared in successive numbers of this Magazine, Mr. James Geikie has replied to the objections which I offered to his views, and also to the views of sequence which I myself advance, by asserting that the seaward ends of glaciers never float; and that my view that “wherever the ice-sheet rested there no deposit occurred, the material produced by its action incessantly travelling outwards to the ice-edge,” is a misconception.

These holes in the ice filled with water are in no way connected with each other, and at the bottom of them we found everywhere, not only near the border, but in the most distant parts of the inland ice visited by us, a layer, some few millimetres thick, of grey powder, often conglomerated into small round balls of loose consistency. Under the microscope, the principal substance of this remarkable powder appeared to consist of white angular transparent grains. We could also observe remains of vegetable fragments; yellow, imperfectly translucent particles, with, as it appeared, evident surfaces of cleavage (felspar?); green crystals (augite) and black opaque grains, which were attracted by the magnet. The quantity of these foreign components is, however, so inconsiderable, that the whole mass may be looked upon as one homogeneous substance.