nearly covers the surface. The individual zoöids are very numerous on the upper side, mostly arranged in rather irregular. elongated, elliptical or oblong systems, composed of many individuals of various sizes. The adult individuals are rather slender and elongated; the slender post-abdomen equalling or exceeding in length the rest of the body, but not more than half the diameter of the thorax and slightly constricted at base. In young individuals, not half grown, the post-abdomen forms nearly half the whole length, and is very slender. The branchial aperture has six, short, round papillæ; the anal is situated a short distance from the end of the body, and has short inconspicuous lower lobes, with an elongated, pointed lobe above. The branchial sac is oblong, with numerous longitudinal and transverse vessels and a broad ventral duct. The stomach is about as broad as long, subglobular, with the ends truncated and the surface covered with numerous, interrupted, longitudinal, glandular ridges. The post-abdomen is nearly filled by the large, elongated ovary, which extends nearly to the posterior end on the dorsal or atrial side, and contains numerous closely packed ovules of comparatively large size, and the conspicuous male organs, extending through the whole length on the ventral or branchial side, in the form of a slightly convoluted, dark colored duct. The posterior end terminates in a small, obtuse papilla. The atrium, or cloacal cavity, contains eggs in which the embryos are well developed, and in some cases the free, tadpole-shaped larvæ. The tunic is speckled with numerous, minute, purplish-brown pigment cells. One of the larger adult individuals measured 30 of an inch. in length; thorax 08; abdomen '06; post-abdomen 16; diameter of thorax 031 to 035; of abdomen about the same; of postabdomen 015 to 020. Amouroucium stellatum Verrill, sp. nov. This species forms large, erect, crest-like plates or fronds, attached at the lower edge to stones and pebbles by short root-like extensions; the outer and upper edges are subacute or rounded, divided into two broad, rounded lobes above. The frond is 2.5 inches high, and about the same in breadth, the thickness varying from 20 to 35 of an inch. The tissue is firm and cartilage-like externally, softer within; surface smooth and glabrous, without adhering sand. The zooids are arranged in nearly circular and pretty regular stellate groups, usually containing from six to fifteen individuals, arranged around a central sub-circular orifice; in contraction the position of each individual is indicated by an oval spot, more transparent than the common tissue, with a small flake-white spot around the branchial orifice. The individual zoöids are elongated and slender; the postabdomen more slender, usually considerably exceeding in length the rest of the body, and but slightly constricted at base; the thorax and abdomen are shorter and stouter than in the preceding species; branchial sac with about 12 transverse vessels; stomach oblong-oval, with numerous longitudinal glandular folds; intestine large. Branchial orifice with six short lobes; anal orifice terminal or nearly so, close to the branchial, with an acute upper lobe. Color, in alcohol, milky white, subtranslucent; zoöids yellowish. One of the larger zoöids measured 31 of an inch in length; the thorax 085; the abdomen 062; the post-abdomen 165; diameter of thorax 045; of post-abdomen 025. Wood's Hole, Mass.,-Prof. H. Ê. Webster. This species is easily distinguished from all the preceding by its large, upright fronds, circular systems, and the regular stellate arrangement of the zoöids, and by its firmer texture and smooth surface. Macroclinum, gen. nov. Allied to Aplidium, forming thick, fleshy masses, of various forms; without cloacal openings or common ducts, each individual having its own branchial and anal orifices, side by side. Systems scattered, usually rather indistinct. Animals elongated, slender; post-abdomen narrow, much longer than the abdomen and thorax taken together, filled with voluminous ovaries, placed on each side of the median duct; eggs small and very numerous; stomach deeply lobed; intestine long, often convoluted; anal orifice terminal or subterminal, near the branchial, subcircular or somewhat bilabiate, the upper side with a rather prominent lobe; branchial with six rounded lobes or short papillæ. Type, M. crater. 23. Savigny included in his genus Aplidium two "tribes,” each containing several species, but differing considerably in strucIn the first tribe, to which the name, Aplidum, should be restricted, the post-abdomen is short and rounded and the ovaries are clustered and contain few large ovules; the anal orifice is on the side of the thorax and distant from the branchial. The second tribe appears to correspond nearly with our genus, Macroclinum, the post-abdomen being very long, with the ovaries arranged along each side; but there is considerable diversity in the arrangement of the anal orifices, if Figure 23.-Macroclinum crater, showing in outline a section through the middle, natural size. The animals are omitted on one side.—Original, by A. E. V. correctly figured. The species are M. effusum from the Gulf of Suez, M. gibbulosum and M. caliculatum from Europe. M. nutans (Johns., sp.) from England, appears to be another species. Macroclinum crater Verrill, sp. nov. Figures 23 to 25. This species forms large, thick, gelatinous, but firm masses, which have a circular outline, with the upper surface deeply concave or cup-shaped. The surface is covered with a thin layer of closely adhering grains of fine sand, which are also diffused throughout the mass. The a branchial and anal orifices are h 25. n g the entire length; the branchial sac has about 16 transverse vessels, with numerous finer longitudinal ones; the branchial orifice has six small papillæ; the anal is terminal, and slightly bilabiate, with the lobe above it broad and usually recurved at the tip. The stomach, in most of the examples examined, was empty and badly contracted; it appears to be deeply lobed. The post-abdomen is very long and connected to the abdomen by a somewhat narrower, short pedicel. A conspicuous median duct extends the whole length, with the voluminous ovaries on each side. The ovules are very small. The common mass is 175 inches in diameter, and 1 high; the largest individuals are 50 to 65 of an inch long, and '06 to 07 in diameter, at the thorax. Color in alcohol translucent yellowish white; the animals. light yellow. Banks of Newfoundland,-T. M. Coffin. Figure 24.-One of the individual animals, extracted and enlarged 7 diameters; a, anal orifice; b, branchial; c, branchial sac; e, stomach; f, intestine; h, heart; o, ovary; q, egg in process of development in the cloacal chamber or atrium; s, spermatic duct.-Original, by A. E. V. Figure 25.-View from the opposite side, showing the thorax and abdomen of another individual, enlarged 10 diameters; g, termination of the intestine, which is filled with focal matter; i, ventral duct of the branchial sac; n, cloacal chamber. With the last species Mr. Coffin otbained another, which is not well enough preserved to admit of accurate determination. It may be a species of Amouroucium, or another Macroclinum. It forms broad incrustations, 2 or 3 inches across and about 25 thick in the center. The marginal portion is thin and covered with adherent grains of sand; the central part is smooth and glabrous, slightly convex. The zooids are about 30 long, with a long post-abdomen, which is not pedicellate, resembling that of A. glabrum. ART. XLV.-Amazonian Drift; by Prof. CH. F. HARTT, of Cornell University. PROF. AGASSIZ has claimed that the structure of the Amazonian valley is very simple; that, from one end to the other, there was laid down in the fresh water lake formed by the damming up of the mouth of the valley, by a glacial moraine, beds of sands, clays and sandstones, filling the valley to the height of several hundred feet above the present level of the river; that, from the bursting of the barrier and the draining of the lake, the uppermost beds were denuded down, and swept off from over a very great part of the valley, leaving only isolated outlines as a series of table-topped hills or serras, like those of Almeirim, Paraúquára, Velha Pobre; that the lake, reduced to a lower level, then threw down over the denuded portion, a sheet of clay, the river finally cutting its channel through this clay and the underlying sand, &c. He did not claim to have found grooved or striated surfaces in the Amazonas, and the only instance of supposed erratics he gives is that of the diorite found on the flanks of the serras of Ereré. Prof. Agassiz gave as a type of the table-topped hills the serra just mentioned. Last summer, in making an examination of the lower part of the Amazonian valley, I visited Ereré and spent a month in its vicinity going over the ground on foot in every direction, and in the most detailed way. The serra does not belong to the system of table-topped hills of which Paraúquára and Velha Pobre are examples. These last and the range of highlands on the south of the Amazonian valley are composed of soft materials; they are perfectly flat on top and descend on all sides by a steep even slope; moreover, the strata composing them are horizontally disposed. Ereré is a short, narrow, irregular ridge about 800 feet in height, several hundred feet lower than the table-topped hills, the top being anything but horizontal. The strata composing it are principally a heavy-bedded coarse white sandstone exceedingly hard, with bands of indurated feldspathic clay. These beds dip to the southeastward (approximately), with an angle in some places of 15 or 20°. On the northern side of the serra and extending close up to its base is an extensive plain composed of a series of coarse shaly sandstones, shales, and cherty heds, quite horizontal, and not participating in the disturbance which the strata of the serra have suffered. These beds contain trilobites of the genus Dalmanites, with species of Spirifer, Orthisina, Chonetes?, Discina, Lingula, Leptocalia, Tentaculites, &c. Specimens of these have been submitted to Prof. Hall who writes me that they indicate a horizon equivalent to the Upper Helderberg. The conclusion seems inevitable that the serra is pre-Devonian in age. The Devonian rocks of the plain are broken through by a perfect net work of dikes of trap now decomposed. The end of a curious low ridge that runs off at right angles from the serra consists of a large mass of 'trap. This has given rise to a great number of boulders of decomposition which lie on the surface or are buried in decomposed rock. They have been carried down the beds of torrents but they are nowhere erratics. To speak broadly, I did not see either at Ereré or in any part of the Amazonas, anything that would suggest glacial action. So far as the province of Para is concerned, the clays, sands, &c. forming the lower lands are far from being uniformly distributed, and are very puzzling to study. The arrangement of the materials varies in different regions, and many of the deposits are local. In part, the lower lands are formed from the wearing down of the great sheet of clays, &c., of which the Almeyrine hills are relics, in part they are of brackish or fresh water origin when the river stood at a greater height; and much is the very recent work of the river. The variegated clays belong to several distinct epochs. Superficially examined they appear to be universally distributed, but it is very far from being the case. It is impossible to recognize beds of clay in the Amazonian valley simply from lithological characteristics. It is sufficient to say that variegated clays of exactly the same appearance and structure, because formed of materials reworked or drawn from the same source, occur in the Devonian, Carboniferous, Tertiary and in half a dozen successive formations of recent times. I have referred the beds of the table-topped hills to the Tertiary. Some of the clays and sandstones of the lower Amazonas may also be later Tertiary; but many are undoubtedly recent, they are full of leaves of modern species. Near Santarem I found a bed of recent fresh water mussels, Castaleas, Hyareas, Unios, &c., whose upper limit was at least fifty feet above the level of the highest Amazonian floods. This is in exact accord with the facts I have given elsewhere-being on the late rise of the Brazilian coast, a rise which extended itself into the interior. Before this rise the land stood much lower than at present; |