cavities have yet been observed in the dorsal valve. It thus becomes evident, that the existence or non-existence of these cavities, is not always a character of generic value. Whether it be so or not, in any particular instance, depends upon the extent to which the cavities are developed. They may be so small and rudimentary, as not to be even of specific value. Or they may be so large, as to constitute good sub-generic characters. I have some specimens which seem to show that small cavities also exist in species that, with our present knowledge, can only be referred to the genus Monomerella. In a general way, therefore, it may be said that these genera are destitute of cavities, but that, ex. ceptionally, they do occur, and that where such is the case, an approach to the genus Trimerella is indicated.

I consider that Obolellina, Monomerella and Trimerella, are merely sub genera of a single great genus, of which the first, as it is the most ancient, and the least specialized, should be regarded as the type. They gradually pass into each other, and no doubt. as the number of species increases, it will become more and more difficult to draw lines between them.

The Canadian species are O. Canadensis, O. Galtensis and 0. magnifica. The second of these, has the muscular impres sions in the dorsal valve of the same form and arrangement as those of the first named. The beak of the ventral valve is very large, its length being one-half that of the body of the shell. It is slightly incurved. The area has three furrows, the peduncular and the two lateral grooves. The muscular impressions are rhomboidal rather than ovate, and confined to the central portion of the shell. There are no cavities under the area.

I am informed that it is now proposed to place O. Galtensis in one of Prof. Hall's unpublished genera, presently to be noticed, along with the species described in the 20th N. Y. Reg. Rep. p. 368, under the name of Obolus Conradi. It seems to me however, that this latter is a Trimerella, or rather one of those forms whose position is near the dividing line between Trimerella and Obolel lina. Prof. Hall has figured the cast of the interior of a ventral valve in Pl. 13, fig. 2, of the work cited. Close to the area there are two short obtuse cones, which are continued towards the front, as two rounded ridges, one on each side of the muscular impressions. The latter extend nearly up to the area, and are separated by a small rounded ridge. These characters are all seen in the cast of the ventral valve of Trimerella. They do not occur at all in either of the three species of Obolellina.

Prof. Hall's fig. 1 represents the cast of the interior of the dorsal valve of his Obolus Conradi, showing that the three muscular impressions are completely concealed by two sub-conical projections, just as they are concealed by the cones in Trimerella. I have lying before me fifteen casts of the interior of O. Galtensis, and in all of them the three scars are entirely exposed as in fig. 6, below. With all due deference, therefore, I think that O. Conradi should be classified in Trimerella rather than in the same genus with O. Galtensis.

FIG. 6. The original figure of O. Galtensis showing the cast of the interior of the dorsal valve. Compare with Fig. 2. The specimen is imperfect but it shows the casts of the groove dd, the two large ovate scars, bb, and the smaller pair, c, of fig. 2.

8. Dorsal valve of Obolellina? magnifica. This was figured in the Report of the Geological Survey of Canada for 1857, published in 1858 as a dorsal valve of O. Canadensis. It is, however, a distinct species. The following is the description.

O? MAGNIFICA, n. sp. Dorsal valve transversely broad ovate; width about one-fourth greater than the length; uniformly and moderately convex; apical angle about 120 degrees; cardinal edges nearly straight, or gently convex for about one-third the length of the shell; sides and front rounded, the latter more broadly than the former. The area seems to be obsolete altogether or merely linear..

The ventral valve is depressed convex with a large beak slightly incurved. Arca with a wide triangular peduncular groove; no lateral furrows. Surfaces of both valves concentrically marked with imbricating lines of growth.

In a specimen, which appears to have been about 20 lines in length, the height of the area is nearly 3 lines.

I place this species doubtfully in this genus, because there is in the interior of the dorsal valve, a distinct muscular pit about one line in front of the beak, which does not occur in either of the other two species. In one well preserved specimen this scar is distinctly seen to be divided into two, by a longitudinal ridge. It may be that it represents the small anterior scar (c. fig. 2) which is certainly variable in form and perhaps, also, in position. In O. Canadensis, for instance, the scar, c, is sometimes a distinct ovate pit, as shown in fig. 2, entirely separated from the two larger scars, bb. In others all three are confluent, or at least in contact, while in one specimen, c, is represented by two elongated grooves, separated by a rounded ridge, extending backwards between, lb. Some of the figures of the English species 0. Davidsoni, seem to show that a pit, like that of O. magnifica, occurs in one of the valves of that species.

O. magnifica occurs in the Black River formation, along with O. Canadensis.

A QUESTION OF PRIORITY.

About three weeks after the above genus was published, I received a letter from Thos. Davidson, Esqr., F.R.S. Brighton, England, informing me that it had been previously named, by Prof. Hall in a pamphlet of 5 pages, dated March, 1871. On this subject I beg to make a few remarks.

Το

When I was appointed to the office I now hold, in 1856, Prof. Hall was engaged on his 3rd vol, Pal. N.Y., which relates altogether to the Upper Silurian fossils of the State of New York. Sir W. E. Logan gave me to understand that I was not to describe any Upper Silurian fossils until Prof. Hall should have completed his volume. It was also understood, that I should not describe any species which might occur in New York and not in Canada. do so was thought to be in the highest degree discourteous and un fair. Species that were found in Canada I could describe, although they might be known to occur in New York also. I have never once transgressed these rules for sixteen years. I have compared a number of collections for parties living in New York but have always declined to describe new species, although frequently urged to do so. There is a person at this present time at work on N. Y. fossils, and I have declined to give him any assistance.

It appears that many years ago, Prof. Hall obtained from Galt, a single specimen of the ventral valve of O. Galtensis. This spe

cies does not occur at all in New York. In the beginning of 1871, Prof. Hall applied to Mr. Selwyn for the loan of the original specimens of Trimerella grandis, stating that he wanted them to elucidate some points in the structure of his Obolus Conradi. I consented to the loan of them, and Prof. Hall was informed by Mr. Selwyn that the genus was then under investigation by Mr. Davidson, Mr. Dall and myself. Shortly afterwards he applied for specimens of Kutorgina and O. Canadensis. I declined to lend the latter as I was then using it. In reply he intimated that he had no desire to take any advantage of me, but only to fortify his own position. It turns out, however, that he was then actually working at O. Galtensis, intending to make a new genus on a Canadian specimen. He did not inform Mr. Selwyn of this fact. Ten months afterwards, I heard from Mr. Davidson that Prof. Hall had proposed a new genus Rhynobolus, on the Canadian specimen. before mentioned, and it then became apparent why he wished to borrow O. Canadensis. A question now arises, whether or not his pamphlet was regularly published, previously to the 29th Dec. 1871, the date of the publication of my genus.

I have made extensive enquiries in the United States and Canada, among those who would have been the first to have received it, had it been regularly published, and cannot find one who had ever seen it previously to the 29th December, 1871. I have heard from the Directors of six Geological Surveys, from the Smithsonian Institution, the Academy of Natural Sciences of Philadelphia, the New York Lyceum of Natural History, the Boston Natural History Society, McGill College and the Nat. Hist. Soc. of Montreal, besides a number of geologists and professors in colleges where geology is taught. The general opinion is that it was not published in the United States at all.

Then as to foreign countries, the only copy I have any certain account of, is the one sent to Mr. Davidson. Another is noticed in the Journal of the Geological Society for February, 1872, but the exact date of its reception is not mentioned. The case stands thus.

It is admitted by all that the only test of priority is publica. tion. By this term we must understand the placing of a book or pamphlet on sale, so that it may be accessible to the public by way of purchase.

On the other hand, when an author only gives away several copies of his work to his private friends, this is not publication,

but private distribution. Should he even send one to a learned society, whose library is private, it would still not be publication. The work would not be accessible to the public.

My genus was openly and fairly published, on the 29th Dec., 1871, in a scientific journal of good standing, and at all times obtainable by purchase.

Prof. Hall's pamphlet was not published, but only privately distributed to a very few parties.

Although the law (that publication in the true sense of the term is the only test of priority,) should, in general, be rigidly enforced, yet in peculiar cases it admits of a considerable amount of flexibility. It should not always be carried out with a strong hand. Circumstances may render it necessary, in order to do justice, that it should be very strictly adhered to as against one of the parties, and more leniently as regards the other. When one of the disputants has proceeded in an irregular manner; has not published his paper in the ordinary way, in a scientific journal or book obtainable by purchase; and when, in consequence of such irregularity, the difficulty to be settled has arisen, he is to blame, and the law should be strictly enforced. If Prof. Hall had brought out his descriptions of Rhynobolus and Dinobolus, in any of the scientific journals of this continent, in March, 1871, I would almost certainly have seen it before the month of December, and would not have published my genus. This unfortunate. collision would not then have occurred. But instead of following the regular mode of publication he resorted to private distri bution, on a most limited scale; not in America but in England. In consequence of this I knew nothing of his genera, until I was informed of them by Mr. Davidson, in a letter which only reached me on the 17th of Jan., 1872, three weeks after my paper was published. It is not, therefore, my fault but his, that a controversy has arisen. Then as regards the Canadian specimen of 0. Galtensis, he should, before he instituted a genus upon it, have given Mr. Selwyn notice; but instead of this, although he was informed that I was working at the group of fossils to which it belongs, he said nothing about it. It is not my fault that he concealed this from us. If the species occurred in New-York, as well as in Canada, he would not have been under any obligation to give notice, but as it does not occur in that State the case is quite different. It is said that shortly after his paper was printed a part of the edition was destroyed by fire. That is his mis