other independent groups which I have first distinguished under the name of synthetic types. Its resemblance to the Trilobites is unmistakable, and very striking. In the first place the head stands out distinct from the thoracic regions, as the buckler of Trilobites; and the large, kidney-shaped facetted eyes recall those of Calymene; moreover, there is a facial suture across the cheeks, as in Trilobites, so that, were it not for the presence of the antennæ, which project from the lower side of the anterior margin of the buckler, in two unequal pairs, these resemblances would amount to an absolute identity of structure. As it is, the pres ence of an hypostome, in the same position as that piece of the mouth is found in Trilobites, renders the similarity to this extinct type of crustacea still more striking, while the antennæ exhibit an unmistakable resemblance to the Isopods.

In view of the synthetic character of these structural features it should not be overlooked that the buckler of our new crustacean, for which I propose the name of Tomocaris Peircei, extends sideways into a tapering point, curved backward over the first thoracic ring, as is the case with a great many Trilobites, The thorax consists of nine rings, seven of which have prominent lateral points, curved backward, like the pleura of Olenus, Lichas, &c. The sixth ring is almost concealed between the fifth and seventh, and is destitute of lateral projections, as is also the ninth. These rings are distinctly divided into three nearly equal lobes by a fold or bend on each side of the middle region, so that the thorax has the characteristic appearance of that of the Trilobites, to which the latter owes its name. The legs are very slender, and resemble more those of the Copepods and Ostracoids than those of any other crustacea. There are nine pairs of them, all alike in structure, six of which, however, the anterior ones, are larger than the three last, which are also more approximated to each other. Besides the legs, there is a pair of maxillipeds attached to that part of the buckler which extends back of the facial suture. These maxillipeds resemble the claw of a Cyclops. All these appendages are inserted in that part of the rings corresponding to the bend of the thoracic lobes; so that, if there exists a real affinity between the Trilobites and our little crustacean, and their resemblance is not simply a case of analogy, we ought hereafter to look to a corresponding position for the insertion of the limbs of Trilobites. I do not remember with sufficient precision what Billings, Dana, and Verrill have

lately published concerning the limbs of Trilobites, to say now what bearing the facts described above may have upon the subject, as lately discussed in The Journal of Science. But of one thing I am satisfied, since I have examined the Tomocaris Peirceithat Trilobites are not any more closely related to the Phyllopods than to any other Entomostracæ, or to the Isopods. In reality, the Trilobites are, like Tomocaris, a synthetic type, in which structural feature of the Tetradecapods are combined with characters of Entomostraca and other peculiarities essentially their

own.

The pygidium or abdomen of Tomocaris is very like the abdomen of the ordinary Isopods with an articulated oar attached sideways and leaf-like respiratory organs upon the under side. The whole pygidium is embraced between the last curved points of the side of the thorax. Owing to these various combinations, I would expect in Trilobites phyllopod-like respiratory appendages under the pygidium only, and slender, articulated legs, with lateral bristles under the thorax, so thin and articulated by so narrow a joint as easily to break off without leaving more than a puncture as an indication of their former presence. It is impossible to study carefully the synthetic types without casting a side glance at those natural groups, which, without being strictly synthetic themselves, have nevertheless characters capable of throwing light upon the whole subject. And in this connection I would say a few words of Apus and Limulus. If I remember rightly, Milne Edwards considers the shield of Limulus as a cephalothorax in which the function of chewing is devolved upon the legs, while he regards the middle region as an abdomen, and the sword-like tail as an appendage sui generis. In the light of what proceeds, I am rather inclined to consider the cephalic shield of Limulus as a buckler homologous to that of the Trilobites, and the middle region as a thorax in which the ring show unquestionably signs of a division into lobes as in Trilobites. The tail would then answer to the pygidium. Apus should be compared with the other crustacea, upon the same assumptions as Limulus.-Ever truly your friend, L. AGASSIZ.

-From the New York Tribune.

DREDGING IN LAKE SUPERIOR UNDER THE DIRECTION OF THE U. S. LAKE SURVEY.-Extensive dredgings were undertaken the past season in Lake Superior, from the U. S. steamer

Search, under the direction of Gen. C. B. Comstock, Superintendent of the Lake Survey. Dredging was carried on from the shallow waters, especially along the north shore, down to 169 fathoms, the deepest point known in the lake. In all the deeper parts of the lake, the bottom, as shown both by the dredging and by the soundings executed by the Survey, is covered with an uniform deposit of clay, or clayey mud, usually very soft and bluish or drab in color. Water brought from the bottom at many points was perfectly fresh; that from 169 fathoms gave no precipitate with nitrate of silver. The temperature, everywhere below 30 or 40 fathoms, varied very little from 39°, while at surface (at the time of the observations, during August) it varied from 50° to 55°. The fauna of the bottom corresponds with these physical conditions. In the shallow waters, the species vary with the varying character of the bottom, while below 30 to 40 fathoms, where the deep-water fauna properly begins, the species seem to be everywhere very uniformly distributed. The deep-water fauna, as might be expected from the unfavorable character of the bottom, is meager, and seems to be characterized rather by the absence of many of the shore species than by forms peculiar to itself. Some of the more interesting species occurring in deep water were Mysis relicta Lovén, at various depths from 4 to 159 fathoms; Pontoporeia affinis Lindst., at nearly every haul from the shallowest to the deepest; a small undescribed species of Pisidium, down to 159 fathoms; several forms of dipterous larvæ, allied to Chironomus, down to the same depth; several species of Lumbricoid worms, of the genera Tubifex, Sœnuris, and an allied genus; and a species of Hydra, which was found from the shore down to 159 fathoms. Of these, the Mysis, Pontoporeia, and Pisidium are identical with species found by Dr. Stimpson in his dredging in Lake Michigan, a short account of which was published in the American Naturalist for September, 1870. The species of Mysis and Pontoporeia I am unable to distinguish from specimens from the Lake Wetter in Sweden. In the Swedish lakes, these species were associated with Idotœa entomon and Gammaracanthus loricatus, marine species, and were supposed by Lovén to have been derived from ancient marine species left in the lake basins by the recession of the ocean. The occurrence of these forms in Lake Superior, so far removed from the ocean, is certainly a very interesting fact in the geographical distribution of species, but one which I will not attempt to discuss

in this brief notice. In the shallow waters many interesting spe cies were obtained. Among these was a new species of Crangonyx, a genus closely allied to Gammarus, and heretofore known only from a few species found in the fresh waters of the old world, which occurred in 8 to 13 fathoms; and at the same depth, species of Lumbricus, Nephelis, Procotyla, Gammarus, Asellus, Limnæa, Physa, Planorbis, Valvata, Sphærium, Pisidium, etc, A full report will soon be published.

S. I. SMITH in Silliman's Journal,

MISCELLANEOUS.

AWARD OF THE WOLLASTON MEDAL TO PROF. J. D. DANA, -Geological Society, February 16.—Mr. Joseph Prestwich, F. R.S., president, in the chair.—The Secretary read the reports of the council, of the Library and Museum Committee, and of the auditors. The general position of the society was decribed as satisfactory, although, owing to the number of deaths which had taken place among the fellows during the year 1871, the society did not show the same increase which has characterised former years. In presenting the Wollaston gold medal to the Secretary, Mr. David Forbes, for transmission to Prof. Dana, of Yale college, Connecticut, the President said: "I have the pleasure to announce that the Wollaston Medal has been conferred on Prof. Dana, of Yale College, Newhaven, U.S.; and in handing it to you for transmission to our Foreign Member, I beg to express the great gratification it affords me that the award of the Council ha fallen on so distingnished and veteran a geologist. Prof. Dana's works have a world-wide reputation. Few branches of geology but have received his attention. An able naturalist and a skilful mineralogist, he has studied our science with advantages of which few of us can boast. His contributions to our science embrace cosmical questions of primary importance-paleontological questions of special interest-recent phenomena in their bearings on geology, and mineralogical investigations so essential to the right study of rocks, especially of volcanic phenomena. The wide range of knowledge he brought to bear in the production of his excellent treatise on Geology, one of the best of our class books, embracing the elements as well as the principles of geology, is well known. His

the

treatise on Mineralogy exhibits a like skill in arrangement and knowledge in selection. In conveying this testimonial of the high estimationin which we hold his researches to Prof. Dana, may I beg also that it may be accompanied by an expression how strongly we feel that the bonds of friendship and brotherhood are connected amongst all civilised nations of the world by the one common, one universal, and the one kindred pursuit of truth in the various branches of science."-Mr. David Forbes, in reply, said that it was to him a great pleasure to have, in the name of Prof. Dana, to return thanks to the society for their highest honour, and for this mark of the appreciation in which his labours are held in England. It had rarely if ever occurred in the history of the society that the Wollaston medal had been awarded to any geologist who had made himself so well known in such widely different departments of the science, for not only was Prof. Dana preeminent as a mineralogist, but his numerous memoirs on the Crustaceans, Zoophytes, coral islands, volcanic formations, and other allied subjects, as well as his admirable treatise on general Geology, fully testify to the extensive range and great depth of his scientific researches.-The President then presented the balance of the proceeds of the Wollaston donation fund to Prof. Ramsay, F.R.S., for transmission to Mr. James Croll, and addressed him as follows:-"The Wollaston fund has been awarded to Mr. James Croll, of Edinburgh, for his many valuable researches on the glacial phenomena of Scotland, and to aid in the prosecution of the same. Mr. Croll is also well known to all of us by his investigation of oceanic currents and their bearing on geological questions, and of many questions of great theoretical interest con nccted with some of the great problems in Geology. Will you, Prof. Ramsay, in handing this token of the interest with which we follow his researches, inform Mr. Croll of the additional value his labours have in our estimation, from the difficulties under which they have been pursued, and the limited time and opportu. nities he has had at his command."-Prof. Ramsay thanked the president and council in the name of Mr. Croll for the honour bestowed on him. He remarked that Mr. Croll's merits as an original thinker are of a very high kind, and that he is all the more deserving of this honour from the circumstance that he has risen to have a well-recognised place among men of science without any of the advantages of early scientific training; and the position he now occupies has been won by his own unassisted exertions. The