The artist who is illustrating a great theme upon a large spread of canvas finds it necessary from time to time to lay down the brush, with which he is accurately filling in the more delicate minutiæ, that he may retreat to a distance and view his picture as a whole. It is essential to the higher development of his art that he should not omit this comprehensive survey. The same thing holds good in Literature and Science, as well as in Art. The historian must, from time to time, take a fresh survey of History as a whole. If he neglect to do so, the group of figures to which he devotes his special attention will certainly not take up its true position among the other groups that appear on the canvas of History. The man of science, also, should not forget that he is, according to his individual bent or capacity, aiding in the construction of a great Philosophy; and he should now and again turn aside from the microscope, or lay down the hammer, to take a more comprehensive survey of that Philosophy, whose aim it is to comprehend and consolidate the widest generalizations of Science.

Dr. Mantell, in his classical work, the “Fossils of the South Downs,” figured two large compressed and lanciform teeth preserved in his collection and obtained from the Chalk at Lewes, as respectively the teeth, of an unknown fish and of a species of Squalus. Similar teeth, and from the same collection, were subsequently figured and described by Prof. Louis Agassiz, who, from external characters chiefly, considered them to have belonged to a Sphyrænoid fish, and he referred them to an American species founded by Dr. Harlan upon portions of jaws with teeth in situ found in a Cretaceous deposit in the State of New Jersey, but described by him as remains of a Saurian, and to which he gave the name of Saurocephalus lanciformis. At the time when Agassiz referred these teeth to Harlan's species, and determined their ichthyic character, he had not seen the American fossils; but he states that these conclusions were subsequently confirmed by Prof. Owen's description and drawings of the microscopic structure, and of teeth of the natural size of the Saurocephalus lanciformis, Harl., in his “Odontography,” p. 130, pl. 55. But Prof. Owen's researches were made upon a genuine tooth of the American fossil sent to him by Dr. Harlan, and not upon an English specimen.

The possibility of change in the position of the Earth's axis seems periodically to attract attention. This is happening now. Professor Haughton has written upon this subject, Sir William Thomson has alluded to it, while two important papers have been read upon it, one by Professor Twisden before the Geological Society, the other by Mr. George H. Darwin before the Royal Society. This article is an endeavour to exhibit to the general reader the assumptions with which they have started, and the results they have obtained.

Notwithstanding the numerous papers which have lately been written on the subject of glacial deposits, there is one question of fact which does not appear to have been satisfactorily decided. I refer to the formation of Till underneath glaciers, concerning the possibility of which somewhat different statements were put forward by two writers in the February Number of the GeologicalMagazine.

1. Arbusculites argentea, P. Murray (Edinb. N. Phil. Journ. 1831, vol. xi. p. 147).—Under the title, “Account of the Arbusculites argentea, from the Carboniferous Limestone of Inverteil, near to Kirkcaldy, in Fifeshire,” a curious paper was published in 1831, by Dr. P. Murray, of Scarborough. The organisms are described as “very delicate vermiform bodies, in fragments of different lengths, shining with metallic lustre, neither articulated nor cellular, and resembling broken bits of silver wire.” The author adds, “It would appear to have been an attached Mollusc, dichotomous at first, but afterwards sending out lateral branches, moderately tapering, and with very distant and obscure (if any) articulations, grooved longitudinally, and composed of a bright silvery cortical case, and a solid axis of carbonate of lime. … It differs decidedly from the Crinoidal animals, which are regularly articulated; and varies nearly in the same degree from the Corallines, etc., by not displaying the cellular structure characteristic of that family.” Dr. Murray ultimately places this fossil amongst the Corallines, selecting for it a provisional resting-place in the third order of the first class of Lamouroux.

I Propose in this paper to give the evidences for the strati-graphical position of this interesting group, both because the task, so far as I am aware, has not been attempted in detail, and because American geologists themselves are not altogether agreed on the subject, some maintaining the equivalence of the group with our Ludlow, while there are a few who regard it as an easterly extension of the Niagara series of Western New York. Having had an extensive practical acquaintance with the fossils of New York, in the State Museum, and having supplemented cabinet study by work in the field, I venture to hope that I may be able to determine the question to the satisfaction of geologists.

I Send as a Supplement to my last communication the subjoined Synoptical view of the species of Wealden Entomostraca, treated of in the March Number of the Geol. Mag., trusting it may prove acceptable to both collectors and systematists.