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an approximation to that of the crag Carcharias, but it differs widely in its relative proportions, and in the presence of lateral denticles.-Its robust form, and the great extent of surface by which it was implanted in the jaw, indicate its having been an organ of prodigious power. Its thickness is about equal to half its width, as seen by the section, fig. 42. That of Carcha

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rias megalodon is only in the proportion of 1 to 4. I am aware that the teeth in the existing species of Carcharias differ considerably in form, according to the position which they occupy in the jaw; but the above proportions will be found to hold good through a series of specimens, and may therefore be regarded as depending upon generic distinction. The edges of the teeth in Otodus are perfectly free from serrations, and the crag specimens of Carcharias appear so, but in the latter their absence depends upon attrition. Some of the squaloid teeth figured in Moreton's Synopsis of the cretaceceous fossils of the United States, probably belong to the present genus.

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Figure 43 is a silicified zoophyte from the Kentish chalk, in which a Cidaris appears very snugly housed, with its

spines in several places projecting through the substance of the organic body which surrounds it, as at (a). It would, I think, be a knotty point to determine, in this instance, which of the two has been the aggressor,—the Ventriculite or the Cidaris. The former cannot have been simply growing upon a dead shell, because the root of the zoophyte is at the small extremity, and the large spines of the Echinus are still in connection with the shell to which they belong. This curious fossil is in the cabinet of my friend Mr. Bowerbank.

ART. V.-On Fossil Infusoria found in the County Down, Ireland.

By James L. DRUMMOND, M.D., Professor Anatomy in the Royal Belfast Institution, President of the Belfast Natural History

Society. WHEN my friend William Thompson, Esq., was at Newcastle (at the base of the Mourne Mountains, County Down) last autumn, he received a specimen of a very light, white, earthy substance, which had been found some time previously in considerable quantity, in that neighbourhood, and a short time ago he requested me to investigate its nature, as he felt assured that it was the same kind of substance as Professor Bailey had found in a bog at West Point, in America, (as stated in Silliman's Journal for October, 1838), and which was composed of fossil infusorial remains. I undertook the investigation, and soon found that this anticipation was right; the whole mass consisting of the siliceous remains of organized microscopic beings, either animal or vegetable. I am not aware that fossil Infusoria have hitherto been detected in the British islands, but if not, their discovery is due to Mr. Thompson, as I have only followed up and ascertained, by microscopical investigation, that the views which he had previously entertained were correct.

The substance alluded to is, when dry, of the whiteness of chalk, but becomes brownish when wet; it is as light as carbonate of magnesia, which it much resembles, but is not acted on by nitric,

muriatic, or sulphuric acids, and is indestructible by fire. The specimen I received was a compact mass, of the shape, and nearly the size, of an ordinary buildingbrick; it could easily be rubbed down into powder, and had a coarse and somewhat fibrous fracture; when a portion was rubbed between the finger and thumb, it had no grittiness, but felt like an impalpable powder, and when it was then blown into the air, it flew about almost like wood-ashes,

Vol. III.--No. 31. N. S,

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I had learned from my friend and assistant in my anatomical demonstrations, Mr. Shaw, that during the past summer, his uncle, Dr. Hunter, of Bryansford (near Newcastle), and himself, had been making chemical experiments on a singular substance which had lately been found in that neighbourhood; that they had proved it to be silex, but could ascertain nothing farther concerning it. On showing the specimen to Mr. Shaw, he at once knew it to be identical with the substance which they had been examining; I accordingly requested him to write to Bryansford, and obtain all the particulars he could concerning it, and the following is Dr. Hunter's answer.

“I should sooner have written, but I waited to procure accurate information respecting the deposit at Lough-Island Reavey.' It was found on lowering the water of the lake by the Bann Company, lying in considerable quantity under a covering of about a foot of boggy soil. It was in a semi-fluid state, of the consistence of thick mud, and could be lifted out with a shovel. It soon dried when laid out on the bank. There is also a stratum of an apparently similar substance found in a mountain valley to the south of Slieve Bernagh, in the midst of the Mourne range. It cuts out and shows itself on the face of a bank covered also with a stratum of peaty soil. There are also detached pieces of what I consider a similar matter occasionally found in the low parts of the alluvial soil of Corrogs, of these I shall endeavour to procure specimens, and if possible myself inspect the place where they are found, and send them to you as soon as possible."

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Magnified views of fossil infusorial remains. On examining many times small portions of the fossil mixed with a little water, on a slip of glass, the whole was found

1 This Lough is a few miles from Bryansford.

to be composed of the bodies represented in fig. 44, of which the long, linear spicula (a) form at least four-fifths. The next most abundant are those marked (6), then (c); those marked (d) are still less numerous, and not always seen, though in some of my examinations the portion of fossil in the microscope consisted of them chiefly. Occasionally confervoid fragments (e) were seen, and frequently minute annular portions (f), while (9) is very rare. These are all the bodies which I have observed; there was no admixture whatever of unorganized matter, and no medium of cement whatever.

The spicular bodies (a) are joints of the Diatoma elongatum, ('Eng. Flora,' vol. v. pt. 1, page 406). This species grows in the utmost abundance in a small drain of clear water, in the grounds of the Royal Belfast Institution, and its joints in the microscope are seen to be precisely similar to the spicular bodies. When the loricated Infusoria are burned to ashes, the latter are found to be their siliceous coverings unchanged; and the same thing occurs in the Diatoma, as was discovered by De Brebisson and Professor Bailey.' On burning the Diatoma elongatum to a red heat, I found it, when cold, to be unchanged in form and appearance, its sharpness of outline being equally well defined as before. The Navicula tripunctata I found equally unaffected by heat, as also some other Infusoria with which I am little acquainted. Of the other bodies in the fossil I as yet know nothing more than their appearance; but I think an examination of the waters in the localities where the deposit is found, would bring them to light in a recent state.

The deposit which I have now described is evidently of the same description as that found by Professor Bailey in the New World, and analogous to what is found in several places of the Old ; viz. the Kieselguhr of Franzenbad, and the deposit in peat-bog near the same place, the Bergmehl of Santa Fiora, &c., which are formed of fossil infusorial remains. 2

Belfast, April 30th, 1839.

See paper of the latter on fossil Infusoria discovered in peat-earth at West Point, in Silliman's Journal for October, 1838.

See Edinburgh New Philosophical Journal, for January, 1837, p. 183.

Akt. VI.-Letter from Prof. Agassiz on the subject of the French Edition of the Mineral Conchology of Great Britain.'

Neuchatel, Mai 15, 1839. MONSIEUR,

Je viens de lire dans votre journal (N. 29) une incrimination odieuse de la part que j'ai prise à la publication que fait dans ce moment M. Nicolet, d'une édition à bon marché de la Conchyliologie Minéralogique de J. Sowerby.Rien ne me parôitroit mieux mérité que les reproches qui m'y sont addressés, si les assertions et les insinuations que renferme cet article n'étoient d'un bout à l'autre perfides ou mensongères. Puisque vous avez accueilli cette accusation dans votre journal, j'attends de votre loyauté que vous y insérerez ma justification dans votre plus prochain No.

Malgré l'immense importance de l'ouvrage de Sowerby sur les fossiles d'Angleterre, cette publication n'a pu trouver qu' un petit nombre d'acquéreurs sur le continent. Aussi le connaissance que j'ai des établissements scientifiques des localités les plus importants d'Europe m'a telle donné la certitude qu'une édition Françoise ou Allemande de cet ouvrage, si elle pouvoit être publiée à meilleur marché que l'original, seroit un véritable service rendu à la science, sans nuire en aucun façon à l'édition originale, qui s'est surtout écoulées en pays Anglois. N'y auroit-il pas dès lors mauvaise foi à représenter une pareille publication comme une piraterie systématique? comme si des traductions d'ouvrages scientifiques ne se feroient pas tous les jours au gré des auteurs, et à plus fort raison après leur mort! et comme si, en fesant ce que vous, auteur d'un journal scientifique, vous devez savoir être de bon droit, je devois causer la ruine des héritiers de Sowerby, en les privant du bénéfice d'une publication dont ils disposent depuis plus de quinze ans, et qui est terminée depuis dix, après avoir reçu deux volumes posthumes. Mais il y a plus, lorsque j'ai engagé un lithographe d'ici,-M. Nicolet,- à faire un Sowerby à bon marché, je lui ai fourni gratuitement la traduction du texte, enrichie de nombreuses additions et corrections. Il est donc absolument faux de dire que l'édition Françoise de Sowerby, dont il s'agit, n'est qu' une mauvaise contrefaçon des planches de l'ouvrage Anglois, accompagnée d'une simple translation du texte. Je n'aurois jamais prêté mon nom à une pareille machination. Je dois donc trouver bien étrange la conduite d'un éditeur d'un journal scientifique qui accueille sans examen de pareilles calomnies, et je déclare positivement mensongères les insinuations

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