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the side opposite, or toward the central axis of the visceral cavity, is more or less deeply folded longitudinally. There are two of these to each ambulacrum, attached along the two lines of pores. There appears to be a fissure extending nearly the whole length in the direction of the dotted line f. One edge

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Fig. 12.-Diagrams of one pair of the hydrospires of a Pentremite,-a, the inner side; b, the outer, or side attached to the shell; f. the fissure. 13. Section across an ambulacrum of a specimen of P. Godoni, enlarged 3 diameters.-, lancet plate; g, ambulacral groove; p, p, pores leading into the hydrospires; h, h, the two hydrospires, in transverse section. 14. Ideal figures of a transverse section through an entire specimen showing the ten hydrospires,- one of the five lancet plates; p, p, pores; r, r, the two branches of one of the radial plates. 15. Summit of P. conoideus, -a, anterior side; g, ambulacral grooves (copied from Dr. Shumard, but with the ovarian pores added).

of this fissure, is attached to the lancet plate, along one side of the line of pores; the other to the shell, on the other side of the row. The pores all enter the hydrospire through this fissure. There are ten hydrospires, connected together in pairs, each pair communicating with the exterior through a single spiracle. The arrangement of the folds varies according to the species. In P. Godoni there are five folds, the outer sides of which are close up to the inner side of the lancet plate, fig. 13. In a specimen of P. obesus Lyon, nearly two inches in diameter at the mid-height, the hydrospires extend

AM. JOUR. SCI.-SECOND SERIES, VOL. XLVIII, No. 142.-JULY, 1869.

inward about three lines, the main body being about one line from the lancet plate. There are five folds, each two lines deep; and thus, if the thin shelly membrane, which constitutes the wall of the hydrospire, were spread out, it would have a width of 22 lines,-and the ten together would form a riband, about 18 inches in length, and nearly two inches wide. The object of the folding is, of course, to confine this large amount of surface to a small space, an arrangement which at once proves the function to be respiratory. Of those figured by Mr. Rofe, P. ellipticus Sowerby appears to have only one fold, P. inflatus, id., shows eight folds in one, and eleven in the other hydrospire of the same ambulacrum. Another specimen figured by Mr. Rofe under the name of P. florealis Say, has five folds situated at a distance from the inner surface of the lancet plate as in P. obesus. From the form of the organ I think that Mr. Rofe's specimen cannot be the species called P. florealis by Say.

If it be granted that these organs are respiratory in their function, then, their five apertures should be called spiracles, -not "ovarian orifices." The large anterior aperture would thus be the oro-anal spiracle. Applying this system of terminology to other groups,-the so-called ovarian orifice of the Cystidea, the homologous aperture of Nucleocrinus, Codaster, Granatocrinus and of the Paleozoic Crinoidea generally (but not of the recent forms), should be styled the oroanal orifice.

I think that the side of an Echinoderm in which the mouth is situated should be called "anterior" even although the anus and the mouth be confluent in one orifice. Most starfishes have but one aperture for mouth and vent and yet it is called the mouth by naturalists generally. Why not call the underside of a star-fish "the anal or posterior side," and the central aperture the "anus ?"

Dr. B. F. Shumard has shown (Trans. Acad. Nat. Sci. St. Louis, vol. 1, p. 243, pl. 9, fig. 4,) that in perfect specimens of P. conoideus Hall, the six summit apertures are closed by several small plates. In a specimen of the same species sent me by Mr. Lyon, in which those plates are partly preserved, I find that there is a small pore in each of the five angles of the central aperture. The five ambulacral grooves enter the inte rior through these pores. I have copied his figure but modified it by adding the pores, fig. 15. He also found that the summit of P. sulcatus, Roemer, was covered with an integument of small plates arranged in the form of a pyramid. From these facts he infers that in all the pentremites the summit apertures will be found in perfect specimens, to be closed in a similar manner.

Dr. C. A. White, at present State Geologist of Iowa, in a paper on the same subject, (Bost. Jour. N. H., vol. 8, pp. 481488,) describes P. Norwoodii Owen and Shumard and P. stelliformis, id., as having a similar structure-but he goes further, he considers the central orifice "not to be the mouth," and I believe that he is the first naturalist who ever published such an opinion. His idea of its function is thus expressed: "It seems more probable that as the ova were germinated within the body, they found their exit through the central aperture, and were conveyed along the small central grooves of the pseudambulacral fields before mentioned, beneath the plated integument, to the bases of the tentacula, where they were developed and discharged as in the true crinoids." I perfectly agree with Dr. White in this view. The central aperture is not the mouth, in fact it is not a natural orifice, but a breach in the summit caused by the destruction of a portion of the vault. The true natural orifices of this part are those that I have discovered in P. conoideus as above mentioned. They are the homologues of the ovarian pores at the bases of the arms of caryocrinus and in part, as I shall show in another part of these notes, of the ambulacral orifices of the true crinoids.

With regard to the structure of the calyx of Pentremites, it is generally supposed that there are only three series of plates-the basal, radial and interradial. Mr. Lyon has advanced the opinion that there are three small plates below those now called the basals (Geol. Ky., vol. iii, p. 468, pl. 11, fig. 1c). I have examined a number of specimens with reference to this point and I think he is right. There are three small pentagonal basals, the two upper sides of each of which are excavated to receive the sub-radials, i. e., those at present designated "the basals." They are, in general, anchylosed to the subradials, but in one of Mr. Lyon's specimens that I have seen they are distinctly separate.

[To be continued.]

ART. IX.-Spectroscopic examination of the Diatomaceœ; by H. L. SMITH.

THE vegetable nature of the Diatomaceæ is now generally admitted, but if any further proof is needed we have it in marked results from the application of the spectroscope. I have been enabled to prove the absolute identity of chlorophyl or the green endochrome of plants with diatomin or the olive yellow endochrome of the Diatomaceæ. The spectrum-micro

scope is now too well known to need any description here. The one I have used was made by Browning of London. It is not at all difficult to obtain a characteristic spectrum from a living diatom, and to compare it directly with that of a desmid, or other plant.

I need not here give the results in detail. Suffice it that from about fifty comparisons of spectra, I can unhesitatingly assert that the spectrum of chlorophyl is identical with that of diatomin.

The spectrum in question is a characteristic one, and is figured below.

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A very black, narrow band in the extreme red, reading at the lower edge, which appears to be constant, about 3 of Mr. Sorby's scale, is too characteristic to be mistaken. There are two other very faint bands, not easily seen, and somewhat more variable in position. The black band in the red is always present, and is remarkably constant in the position of its lower edge. In making comparisons of spectra it is of the utmost importance that the slit of the spectroscope should be absolutely in the focus of the achromatic eye lens. If this be not attended to, there will be a slight parallax; and bands really identical in position, e. g., those of blood (scarlet cruorine), will not absolutely correspond when two spectra are formed, one from blood on the stage of the microscope, and the other from the same on the stage of the eye-piece.

The dark band of the chlorophyl spectrum is slightly variable in width-and the action of acids and alkalies sometimes causes a slight displacement, the former raising (moving toward the blue end) and the latter depressing. The endochrome of a diatom after treatment with acid, is green, and the acid, in this case, produces scarcely any displacement of the band, which may be observed even in the dark reddish mass of the dead diatomaceæ, almost identical in color, with the ferrous carbonate, so often found in bogs where the larger diatoms are abundant; and what is more remarkable, is, that the carbonate gives no absorption bands at all. As a general rule, alcoholic solutions of chlorophyl and diatomin have the band slightly depressed, reading 1 to 1 on the interference scale.

ART. X.-Note on Wollongongite, a remarkable hydro-carbon found in the Wollongong District of the Illawarra Coal Field, N. S. Wales; by B. SILLIMAN.

In the course of a research conducted by Prof. Wurtz and myself, lately, on the Hydro-carbon Gas Process, my attention was recalled to a peculiar kind of cannel coal from Australia which was brought to this country in 1866, by Mr. Hall of Australia, from whom I obtained my first knowledge of its existence. As it turns out on examination to be by far the most remarkable substance of its class hitherto discovered I propose to describe it.

It is found in the Wollongong district of the Illawarra Coal Field, New South Wales, and in the range known as the Kembla Mountains, or Blue Mountain range. The locality appears to be of recent discovery, as the section taken down from Mr. Hall's dictation is quite different from any section given by Prof. Dana in his account of the Illawarra coal field.* Mr. Hall's enumeration of the strata was as follows.

150 feet superincumbent sandstones.

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Associated with the bituminous shales is a seam of 18 inches of a semi-elastic material resembling mineral caoutchouc which cuts easily with a knife, is easily kindled by a match and yields the odor of a candle when extinguished. It affords about 60 gallons of crude oil. I failed to note its position in the section.

The only account we have seen of the geology of this region is that given by Prof. James D. Dana, in his Report on the Geology of the Countries visited by Wilkes's U. S. Exploring Expedition, pp. 449, et seq.; accompanied by a map of the Illawarra coal field, in which the Wollongong mineral exists. This remarkable mineral was discovered long subsequent to the date of Prof. Dana's explorations in 1840. The writer examined and analyzed the coals brought home by Prof. Dana from Australia, which analyses are published on page 476 of the Report quoted. But among them there was nothing at all resembling the remarkable body now for the first time, as he believes, introduced to the knowledge of gas chemists.

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