but interrupted and immense, when the starting point is consid ered. The physical constitution of man has naturally benefitted by it. The details contained in the treatise, of which the present paper forms the introduction, prove that the human race has been gradually gaining in vigor and strength since the remotest antiquity. The domestic races also, the dog first, then the horse, the ox, the sheep, have shared in this physical development. Even the vegetable soil has been gradually improving since the stone-age, at least in Denmark.

And yet there are persons who deny all general progress, seeing everywhere nothing but decay and ruin, like that worthy specimen of a northern pessimist, who exclaimed, "see how man is degenerated, he has even lost his likeness to the monkey!"

ART. III.-On a new genus of Patelliform shells from the Cretaceous rocks of Nebraska;t by F. B. MEEK and F. V. HAYDEN. (With a plate.)

Genus ANISOMYON, M. & H.

Etym. vioos, unequal;

or, muscle; in allusion to the unsymmetrical muscular scar.

PLATE I.

Generic characters.-Shell very thin, patelliform, or obliquely conical, with an ovate, oval, or circular base; margins entire; surface nearly smooth, or only marked by obscure lines of growth, crossed on some species by fine radiating striæ; summit more or less elevated, located between the middle and the anterior end, sometimes nearly central,-immediate apex very small, and abruptly curved backwards, but not spiral; interior without a projecting lamina or other appendage. Muscular scar irregularly horse-shoe shaped, enlarged at the extremities, with the open part directed towards the shorter end of the shell; becoming abruptly attenuate, or broken into a row of minute oval or circular spots on the right posterior side;-anterior extremities connected by a slender line, which usually passes across just in front of the summit.

This agrees perfectly with the testimony of statistics. See Quetelet, Sur l'homme et le developpement de ses facultés. Paris, 1835, ii, 271. This work of first-rate merit is very near akin to archeology. Mr. Quetelet has just published a new work which will certainly be even more remarkable than the first, and which the author of the present paper regrets not having had within his reach.

The specimens belong chiefly to the collections brought from Nebraska by Lieut. G. K. Warren, U. S. Top. Eng. Full illustrations and descriptions of the species will appear in his report.

SECOND SERIES, VOL. XXIX, No. 85.—JAN., 1860.

On the left side of the shell, the anterior extremity of the muscular impression (a, fig. 2 and 3, of Plate I.) is generally not so much enlarged as on the right, but sometimes extends slightly farther forward; posteriorly it passes around in the form of a a band to the middle of the slope behind (b, fig. 2 and 3), where it is abruptly enlarged and curves upwards. From this point to the larger anterior termination on the right side, there is usually only a slender line (c, fig. 2), which is not always quite connected with the enlarged extremity of the band-like part coming around from the left side. Generally this slender line is nearly or quite entire, while in other specimens, even of the same species, it is broken into a series of minute scars as seen at c, fig. 3, and in some instances it seems to be entirely obsolete, so as to leave the enlarged anterior extremity on the right, quite isolated.

In most instances, the specimens are found with the small apex (d, of fig. 1) broken or worn away, in which condition its former existence would scarcely be suspected. In at least one species (A. borealis) this small apex seems to be perforated in the end, the minute aperture being circular, and about large enough to fairly receive the point of a pin. This may be due to accident, but the thickened and smooth margin of this little opening, as seen under a magnifier, has very much the appearance of a natural orifice. We are not sure that this exists in the other species, but suspect it does. In two of the species A. borealis, and an undescribed form, there are six equidistant impressed hair lines radiating from the summit down the sides, nearly or quite to the margins, but as there are no traces of such lines on some of the others, presenting the same internal characters, we infer they can scarcely be regarded as a generic character.

From the foregoing description it will be seen that the group of shells we propose to include in this genus, although having the form of Patella, present striking differences in the unsymmetrical character of the muscular scar, indicating fundamental peculiar ities in the structure of the animal, while they are all much. thinner and smoother shells than we usually see in that genus. In some specimens, where there appears to be a complete break in the muscular scar on the right posterior side, there would seem to be some analogy to the genus Siphonaria, but as we observe no traces of a siphonal groove passing through this gap, nor any fold in the margin opposite it, and the slender portion of the muscular impression usually passes nearly or quite across, it is scarcely possible any organ such as exists in Siphonaria, could have been extruded there.

The more convex species, such as A. borealis, are somewhat similar externally to some species of Hipponyx, but to say noth

ing of other differences, the fact that the open extremity of the horse-shoe shaped muscular scar in our shells is always turned towards the shorter end, or in other words, that the apex is placed in front of the middle instead of behind it, shows they have no affinities to that or any allied genus.

They would then seem to be perhaps more nearly related to Acma and Gadinia than to any other of our existing mollusca, since in both these genera the animal is more or less unsymmetrical, the former having the branchial plume exserted from the right side of the neck, and the latter a siphon occupying a groove on the right just in front of the anterior extremity of the muscular scar, which is shorter on that side than on the other. Our shells, however, differ from these genera in the peculiar attenu. ate or interrupted character of the muscular impression on the right posterior side, and the folding back of the apex.* In the .thinness of the shell and the nature of the surface, they are most like Acmaa, with which we at first thought them probably identical, but adopting the opinion of M. d'Orbigny that this genus is synonymous with Helcium of Montfort, we referred them provisionally to the latter as the older name. Not long afterwards we observed the peculiar character of the muscular impression on an internal cast of one of the species, but at first supposed it merely due to some accident; subsequently however, we ascertained that it exists in five clearly distinct species, and cannot be regarded as an accidental or specific character.

It is probable many of the Cretaceous and Jurassic species that have been referred by different authors to the genera Patella, Acmoa, Helcium, &c., will be found to possess the internal characters of this genus. Judging from the figures of the Cretaceous and Jurassic species of patelliform shells we have seen in published works, specimens showing the muscular scar, have rarely been found. We have observed the characters of this genus in the following Nebraska species:

ANISOMYON BOREALIS, (=Hipponyx borealis, Morton, 1842=
Helcium carinatum, Meek & Hayden, 1856).

A. SEXSULCATUS, (=Helcium sexsulcatum, M. & H.).
A. ALVEOLUS, (=Helcium alveolum, M. & H.).

A. PATELLIFORMIS, (=Helcium patelliforme, M. & H.).
A. SUBOVATUS, (=Helcium subovatum, M. & H.).

Washington, D. C., Nov. 20, 1859.

* Dr. A. A. Gould, the well known conchologist of Boston, to whom we sent sketches of these shells, writes that he concurs with us in regarding them as being clearly distinct from all the recent genera to which such fossil forms are usually referred.

ART. IV.-General account of the results of the discussion of the Declinometer observations made at Girard College, Philadelphia, between the years 1810 to 1845, with special reference to the eleven year period; by A. D. BACHE, Superintendent of the U. S. Coast Survey.

[Communicated to the American Association for the Advancement of Science, by authority from the Treasury Department.]

It is proposed to give here in outline the results of an investigation of the magnetic observations made with the declinometer, between the years 1840 to 1845, at the Girard College observatory, with special reference to the eleven year period in the amplitude of the solar-diurnal variation and the disturbances of the magnetic declination. Prof. Henry, Secretary of the Smithsonian Institution, has kindly offered to publish the memoir in full in the Smithsonian Contributions to Knowledge. It is my intention to pursue the discussion by taking up the investigation of the lunar influence on the same magnetic element.

In coöperation with the scheme adopted at the British Colonial Observatories, a series of magnetic and meteorological observations were made at the Girard College observatory with instruments purchased under the direction of the trustees of the College, the observations being made under the patronage of the American Philosophical Society, and finally completed for the use of the Topographical Bureau of the War Department. These observations were made under my direction and superintendence. The series commenced in May, 1840, and with short interruptions terminated in June, 1845, thus furnishing a five years series of magnetic observations taken bi-hourly up to Oct. 1843, and after that date hourly. The readings of each magnetic element were united into means, and were also presented graphically (in the fourth volume of the record). This was done under my direction by J. Ruth, Esq., but owing to other laborious duties the record could not be submitted to a more complete reduction. I have now resumed the subject by the assistance of Charles A. Schott, Esq., Assistant in the Coast Survey, by whom, under my immediate direction, and as my assist. ant in this special matter, the present paper has been prepared.*

Although other magnetic observatories furnish by their judicious geographical location, a basis for the generalization of their results, it is nevertheless desirable to obtain results from intermediate observatories as confirmations or as corrections. In the investigation of the disturbance-law at Point Barrow, when compared with the same at Toronto, a very remarkable mutual

It may be proper to state that this work has been performed out of Office hours, and at my own expense.

relation of the law at these stations resulted from such a comparison, and farther examination may bring to light other dependencies of a mutual character.

According to the latest determination the position of the Girard College observatory is in latitude 39° 58′ 23′′ (north), and in longitude 75° 10′ 05′′-5h 00m 403 west of Greenwich. From it Toronto bears 38° 45' west of north (true) and is distant about 334 statute miles.

It is proposed specially to investigate the law of the eleven year period, or, as it is more frequently called, the decennial period, there being yet an uncertainty as to its precise length. It is supposed to have some direct or indirect connection with the solar spot period, which correspondence, according to late investigations by Prof. R. Wolf, is so close as even to exhibit analogous disturbances. The following discussion will afford a contribution towards the determination of the epoch of the occurrence of a minimum in certain phases of the magnetic variation and disturbances, corresponding to a minimum of the solar spots. The method of reduction is substantially the same as that adopted by General Sabine. Earlier investigations of Dr. Lamont and those by Mr. Kreil differ from his in not including the discussion of the disturbances in connection with the period in question.

As long as the magnitude of the deflection remains the only criterion by which a disturbance may be recognized as such, the adoption of any limit of deviation from the normal value of the same hour, month and year, must necessarily remain in some measure arbitrary, or, in other words, there must always remain after the separation of the disturbances a certain small amount of their effect in the remaining regular diurnal progression. To effect the separation, Peirce's criterion has been used with entire success. After a preliminary investigation as to the number of disturbances separated, the limit, as pointed out by the criterion, or a deviation of 8 scale divisions (or 3'6 of arc) has been adopted in the present discussion, as constituting a disturbed observation. Accordingly all observations differing by that amount or more from the mean monthly value of their respective hour were marked by a pencil line. Next a new hourly mean was taken, omitting values so marked, and each observation was again examined in reference to deviation from this new mean. This process was repeated when necessary, so that in all cases, values differing eight scale divisions or more from the mean were excluded. The last mean thus obtained for each observing hour and each month has been called "the normal." These values have been tabulated and are given for each month and year separately, together with such corrections as the omissions or interruptions demanded. The bi-hourly, and afterwards the hourly readings (and their means) were made 191m after the hour so as to correspond to an even Göttingen hour (diagram A).