gated and sub-conic insculptation, forming a series, whose pointed apices almost unite along the longitudinal dorsal ridge. These segments are finely bordered along their posterior articulating edges by an elevated and continuous marginal rim, extending to the lateral extremities of the shell. The cephalic depression is likewise margined by an obtusely elevated border. Each segment of the thorax gives origin, beneath, to a pair of ponderous angulated legs, composed of the ordinary parts. The three anterior pairs project themselves forward, and are closely compressed upon the inferior surfaces of the three foremost segments; they are monodactyle, with the nails incurved upon the anterior edges of the rather largely inflated penultimate joint. Each joint is furnished at its articulating extremity with rigid spines; the inner edges of the penultimate joint, together with those of the three adjoining, are provided with a double row of tufted ciliæ, disposed diagonally, and much resembling in appearance the arrangement of hairs in an ordinary brush. The four posterior pairs of legs are directed backwards, strongly triangu late, stout and ponderous, terminating by a slightly curved nail; their length is nearly equal, but they gradually increase in thickness as they recede toward the tail. The basal joints are large and inflated; the remainder regularly angulate. The extremities of the articulating joints, and edges of the two inferior angles, are each provided with a series of tufted and rigid spines.

The post-abdomen is composed of five segments. The four anterior ones are much smaller than those which constitute the thorax, but greatly resemble them in form, being ornamented on their superior surfaces with similar insculptations, though but slightly defined. Each of these segments is provided beneath with a pair of articulated pedicels, which furnish a support to the bifoliated branchial leaflets. These leaflets are arranged longitudinally one upon the other, and are entirely concealed by the biarticulated plates of the caudal segment; they are suboviate and elongate: the outer ones smaller than those which they cover, and are nearly surrounded by a fringed cilia, most conspicuously developed along their inner margins. The second pair are each supplied with an elongated style, extending almost to the termination of the caudal segment. The terminating segment is large and triangular, giving attachment to the biarticulated plates at a single point on its outer margins near the base, which enables the animal to close them together in a line along its centre beneath. These plates are about the length of the segment, and of a triangulate form, each one having near its termination a small oval articulation. The segment and marginal plates are slightly inflated along their external edges, producing an obtusely elevated border.

SECOND SERIES, VOL. XXII, NO. 66.—NOV., 1856.

The segments constituting the thorax and post-abdomen are supplied by a central, angular, and elongated knob, which, when united, form a prominent dorsal ridge, gradually diminishing in its backward course, and forming a sharp elevated line along the caudal segment, terminating at its extremity in a short and obtusely pointed spine.

This beautiful crustacean furnishes to us another close approximation to the long lost family of the Trilobite. I procured them from the southern shores of the New South Shetland Islands. They inhabit the bottom of the sea, and are only to be obtained when thrown far upon the shores by the immense surges that prevail when the detached glaciers from the land precipitate themselves into the ocean.

Extracts from the Remarks of Dr. Eights on the New South

Shetlands.

After landing at several places along the coast and spending some days at Staaten Land, we proceeded to the new South Shetland Islands, whieh are situated between 61° and 63° of south latitude, and 54° and 63° west longitude. They are formed by an extensive cluster of rocks rising abruptly from the ocean, to a considerable height above its surface. Their true elevation cannot easily be determined, in consequence of the heavy masses of snow which lie over them, concealing them almost entirely from the sight. Some of them however rear their glistening summits to an altitude of about three thousand feet, and when the heavens are free from clouds, imprint a sharp and well defined outline upon the intense blueness of the sky: they are divided everywhere by straits and indented by deep bays, or coves, many of which afford to vessels a comfortable shelter from the rude gales to which these high latitudes are so subject.

The shores of these islands are generally formed by perpendicular cliffs of ice frequently reaching for many miles, and rising from ten feet, to several hundred in height. In many places at their base, the continued action of the water has worn out deep caves with broadly arched roofs, under which the ocean rolls its wave with a subterranean sound that strikes most singularly on the ear; and when sufficiently undermined, extensive portions crack off with an astounding report, creating a tremendous surge in the sea below, which as it rolls over its surface, sweeps everything before it, from the smallest animal that feeds on its shallow bottom, to those of the greatest bulk. Entire skeletons of the whale, fifty or sixty feet in length, are not unfrequently found in elevated situations along the shores many feet above the high water line, and I know of no other cause capable of producing this effect. Whales are very common in this vicinity.

The rocks are composed principally of vertical columns of basalt, resting upon strata of argillaceous conglomerate; the pil lars are united in detached groups, having at their bases sloping banks constructed of materials which are constantly accumulating by fragments from above. These groups rise abruptly from the irregularly elevated plains, over whose surface they are here and there scattered, presenting an appearance to the eye not unlike some old castle crumbling into ruin, and when situated upon the sandstone promontories that occasionally jut out into the sea, they tower aloft in solitary grandeur over its foaming waves; sometimes they may be seen piercing the superincumbent snow, powerfully contrasting their deep murky hues with its spotless purity. Ponds of fresh water are now and then found on the plains, but they do not owe their origin to springs, being formed by the melting of the snow.

The rocky shores of these islands are formed of bold craggy eminences standing out into the sea at different distances from each other, from whose bases dangerous reefs not unfrequently lie out for several miles in extent, rendering it necessary for navigators to keep a cautious watch, after making any part of this coast: the intervals between these crags are composed of narrow strips of plain, constructed of coarsely angulated fragments of every variety of size, which at some previous period have fallen from the surrounding hills. They slope gradually down to the water terminating in a fine sandy beach: a few rounded pieces of granite are occasionally to be seen lying about, brought unquestionably by the icebergs from their parent hills on some far more southern land, as we saw no rocks of this nature in situ on these islands. In one instance, I obtained a bowlder nearly a foot in diameter from one of these floating hills. The action of the waves has produced little or no effect upon the basalt along this coast, as its angles retain all the acuteness of a recent fracture, but where the conglomerate predominates, the masses are generally rounded.

The color of the basalt is mostly of a greenish black. The prisms have from four to nine sides, most commonly however but six, and are from three to four feet in diameter; their greatest length in an upright position above the subjacent conglomerate is about eighty feet. Their external surfaces are closely applied to each other, though but slightly united, and consequently they are continually falling out by the expansive power of the congealing water among its fissures. When they are exposed to the influence of the atmosphere for any length of time, they are for a small depth of a rusty brown color, owing no doubt to the iron which they contain becoming partially peroxydized: sometimes they are covered by a thin coating of quartz and chalcedony.

Clusters of these columns are occasionally seen reposing on their side in such a manner as to exhibit the surfaces of their base distinctly, which is rough and vesicular. When this is the case they are generally bent, forming quite an arch with the horizon. Where they approach the conglomerate for ten or twelve feet, they lose their columnar structure and assume the appearance of a dark-colored flinty slate, breaking readily into irregular rhombic fragments: this fine variety in descending gradually changes to a greenish color and a much coarser structure, until it passes into a most perfect amygdaloid, the cavities being chiefly filled with quartz, amethyst and chalcedony. Sometimes an interval of about forty or fifty feet occurs between these columns, which space is occupied by the amorphous variety elevated to some considerable height against them; their edges in this case are not at all changed by the contact.

The basis rock of these islands, as far as I could discover, is the conglomerate which underlies the basalt. It is composed most generally of two or three layers, about five feet in thickness each, resting one on the other and dipping to the southeast at an angle of from twelve to twenty degrees. These layers are divided by regular fissures into large rhombic tables, many of which appear to have recently fallen out, and now lie scattered all over the sloping sides of the hills, so that the strata when seen cropping out from beneath the basalt, present a slightly arched row of angular projections of some considerable magnitude and extent.

These strata are chiefly composed of irregular and angular fragments of rock, whose principal ingredient appears to be green earth, arranged into both a granular and slaty structure, and united by an argillaceous cement; the whole mass when moistened by the breath giving out a strong argillaceous odor. The upper portion of this conglomerate for a few feet, is of a dirty green color, and appears to have been formed by the passage of the amygdaloid into this rock, the greenish fragments predominating, and they are united to each other principally by a zeolite of a beautiful light red or orange color, together with some quartz and chalcedony; a few crystals of lime cause it to effervesce slightly in some places. These minerals seem in a great measure to replace the earthy cement. In descending a few feet farther, the green fragments gradually decrease in number and become comparatively rare, the minerals also give place to the cement until the whole mass terminates below in a fine argillaceous substance, with an imperfect slaty structure and a spanish-brown aspect.

This rock being much softer in its nature than the basalt and more affected by decomposing agents, the number of fragments are consequently greater in proportion, and much more finely

pulverised, forming the little soil which supports some of the scattered and scanty patches of vegetation on these islands.

The minerals embraced in this rock are generally confined to its upper part where it unites and passes into the incumbent amygdaloid, and many of them are also in common with that rock. They consist chiefly of quartz, crystalline and amorphous, amethyst, chalcedony, cacholong, agate, red jasper, felspar, zeolite, calcareous spar in rhombic crystals, sulphate of barytes, a minute crystal resembling black spinelle, sulphuret of iron and green carbonate of copper.

The only appearance of an organized remain that I anywhere saw, was a fragment of carbonized wood imbedded in this conglomerate. It was in a vertical position, about two and a half feet in length and four inches in diameter: its color is black, exhibiting a fine ligneous structure, and the concentric circles are distinctly visible on its superior end; it occasionally gives sparks with steel, and effervesces slightly in nitric acid.

There are a number of active volcanoes in the vicinity of these islands, indications of which are daily seen in the pieces of pumice found strewed along the beach. Capt. Weddel saw smoke issuing from the fissures of Bridgeman's island, a few leagues to the northeast. Palmer's land is situated one degree south: what little is known of it, which is only a small portion of its northern shore, contains several. Deception island also one of this group, has boiling springs, and a whitish substance like melted feldspar exudes from some of its fissures.

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ART. XXXV.-Description of a large Bowlder in the Drift of Amherst, Massachusetts, with parallel striæ upon four sides; by Professor EDWARD HITCHCOCK.

IN grading one of the streets in Amherst last year, the surface of a large bowlder, or ledge, in front of the residence of Hon. Edward Dickinson, was brought to light, on which numerous rather fine but distinct striae were exhibited, whose direction corresponds essentially with that taken by the drift agency in this region, viz., south a few degrees east. This fact led me to suspect the rock to be the top of a ledge: but on probing the earth around, I found it to be a bowlder. The present summer I proposed to my class in Geology, (which is the Junior Class in College), to dig around the specimen, and try to remove at least the top of it to the vicinity of the Geological Cabinet, about half a mile distant, where it might serve as a fine example of striæ to future classes. They promptly engaged in the enterprise, and on digging around the specimen, found it to be of an oblong