The production of organic matter by phytoplankton in the waters in and around the northern Marshall Islands is extremely low. The amount of plankton swept across the reefs of these islands by the wind‐driven currents is grossly inadequate to support the animals living on the reefs. The reef community, consisting of attached algae and animals, is self‐supporting; all the algae produce at least as much organic matter as all the animals consume. The rate of production of organic matter by an atoll as a whole ‐ water, reef, and bottom ‐ is several times as high as that of the surrounding sea, and permits maintenance of a marine population considerably denser than that of the ocean. The maximum possible rate of growth of the reef is found to be 1.4 cm per year.

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The DORSO-CENTRAL PLATE, (Pelvis of MUUr), PI. \. fig. 1. n, is convex externally, with the angles of the pentagon, which it forms, tm-ned upwards, so that its figure becomes somewhat circular when viewed in connection vdth the plates which it supports. Externally, in the centre, is a circular depression finely striated in radii, for the attachment of the column. A central perforation preserves the communication between the column and body of the animal. The Perisomic plates, (Scapuhe, Miller), PI. \.fig. 1. i, h, are five in number, which adhere to each other by theii* lateral edges. Their lower edges are somewhat orbicular, and their whole contour rounded, so that the perfect animal, instead of presenting a conspicuous pentagonal appearance, as stated by Miller, is only slightly of that figure. Abdoiniinal plates.-The integument which extended over the abdominal cavity was strengthened and protected by numerous smooth, chiefly hexagonal, plates, fi-om which proceeds the elongated proboscis, which is also covered-with smooth plates of similar form. Proboscis.-The figiu'es 1. and 2. e, /, j>, and q, PL 1. are liighly interesting, as bemg faithful representations of that singular organ, the proboscis or oral tube, and which has never been noticed by previous observers as appertaining to this species. In some PLATVCRINID.E. PLATYCRINITES. of single joints for a short distance above tlie points of bifurcation, which structure is succeeded by a double series of joints beautifully articulated into cacli other, the salient angles of one set enterhag into the retmng angles of the adjoining set. (Vide PI. 1.) By this arrangement the greatest possible flexibility, combmed with the requisite strength, PLATYCUINII).?;.

No abstract

The vertical distribution along the equator in the Pacific of temperature, salinity, density, oxygen, and phosphate, from the sea surface to 1000 meters, and the anomaly of the dynamic height of the sea surface and other isobaric surfaces above the 700‐decibar surface are shown. In each of the figures, the available data have been partitioned according to the date of the observation into two periods, July to December and January to June, which are designated in the text as summer and winter, respectively. The figures include data from stations within one degree of latitude north or south of the equator between 110°W and 135°E longitude. The surface of the sea, relative to the 700‐db surface, slopes upward, east to west, approximately 0.8 dynamic meters; the value for the slope is 5.0 × 10−8 during both summer and winter. The longitudinal pressure gradient does not extend much below the layer of relatively large vertical density gradient. At the depth of σ = 26.5, 250–300 m, relatively little east‐west slope is evident. In the surface layer (sea surface to top of the thermocline), temperatures along the equator are lower in the eastern Pacific during both periods; the thermocline is comparatively level west of the 180th meridian, sloping upward to the east of this longitude. Temperatures are appreciably lower and concentrations of inorganic phosphate are higher in the surface layer in the eastern Pacific during the summer, both reflecting the temporal and longitudinal variations in divergence and upwelling. The oxygen minimum, centered at a depth of approximately 450 m, is a continuous feature from 100°W longitude (eastern limit of the profiles) to near 170°E longitude, with the lowest concentrations in the east (≤ 0.5 ml/L) increasing to 1.5 to 2.0 at the westward limit. West of 170°E longitude, concentrations at 450 m rapidly increase to 3.0 ml/L.

No abstract

Cruise 15 of the M.V. Hugh M. Smith consisted of four consecutive lines of oceanographic stations along 140°W longitude between 8°N and 7°S latitude. Geostrophic calculations show that during a five‐week period the maximum eastward velocity component in the Countercurrent progressively increased from 63 to 120 cm/sec and the volume of flow increased from 18.3 to 22.6 X 106 m3/sec.In spite of these short‐term variations, the Equatorial Countercurrent in the central Pacific is remarkably predictable in latitude and general physical characteristics.

The eastern reefs of Rongelap Atoll, composed of animals and attached algae, produce more organic matter than they consume. The productivity per unit area is considerably higher than that of adjacent waters or any^other open marine areas. The zooxanthellae of the corals make a substantial contribution to the whole production, so that per unit of weight, actively growing reef corals may photosynthesize as fast as lithothamnia Review of work on other coral reefs indicates that these communities are generally self-maintaining. PLATE 80. Crania sp. and Thecidellina congregata.81. Thecidellina maxilla and Argyrotheca sp.