. Bulletin - United States National Museum. Science. Fig. 16.—a, Balanus improvisus x 3, quinnepiac, mass.; 6, B. ebueneus x 2, ocean city, md., to ILLUSTRATE DIFFERENCE IN THE KADH. also of a rather brighter yellow. The largest specimens which I have seen are those from the Plata and those attached to a ship from the West Indies, and they had a basal diameter of of an inch—from to of an inch is the more usual full aver- age size. Scuta, with the lines of growth but little prominent; articular ridge prominent but little reflexed; adductor ridge straiglit and very prominent, varying
. Bulletin - United States National Museum. Science. Fig. 16.—a, Balanus improvisus x 3, quinnepiac, mass.; 6, B. ebueneus x 2, ocean city, md., to ILLUSTRATE DIFFERENCE IN THE KADH. also of a rather brighter yellow. The largest specimens which I have seen are those from the Plata and those attached to a ship from the West Indies, and they had a basal diameter of of an inch—from to of an inch is the more usual full aver- age size. Scuta, with the lines of growth but little prominent; articular ridge prominent but little reflexed; adductor ridge straiglit and very prominent, varying a little in its distance from the articular ridge; there is scarcely any depression for the lateral depressor muscle; the upper internal sm-face of the valve is roughened with ridges. Terga, v/ith a moderately deep longitudinal fmTow; spur short, rather narrow, with the end rounded, placed at less than its own width from the basiscutal angle; in the Rio Plata specimens the spur is close to this angle; the basal margin is gener- ally straight on opposite sides of the spur, but sometimes on the carinal side is a little hollowed out. The lines of growth are upturned along the carinal margin, which consequently is a little protuberant, but to a varying degree. The crests for the depressors are extremely distinct and prominent. In the varieties ha\'ing the basi- carinal margin hollowed out, and the carinal margin protuberant, there is a marked resemblance to the peculiar tergum of B. ehurnexis. Walls: The parietal pores are tolerably large and are crossed by numerous trans- verse septa; the longitudinal septa are very finely denticulated at their bases, but occasionally almost smooth. The radii are, as stated, extremely narrow, and very remarkable from their smooth rounded edges; their septa are barely denticulated. The alae are remarkably protuberant; they have their summits much less oblique than those of the radii, and sometimes they are almost parallel to the basis; their 4
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