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Show 1903.] MARINE FAUNA OF ZANZIBAR. 139 MARPHYSA MOSSAMBICA Peters. (Plate XV. figs. 7-10.) Marphysa novce-hollandice Grube, Annulata Semperiana, p. 165. M. mossambica Gravier, Nouv. Arch. Mus. de Paris, 1900; also Kinberg &, Peters. The most complete description of this species is that recently given by Gravier, following on, and adding figures to, that of Grube. The species occurs abundantly in Chuaka Bay, Zanzibar-, living in deep burrows where the sand is of some consistence, i. e. well above low-water mark. In obtaining specimens for bait, the natives dig pits two or three feet deep, scooping away the sand from the circumference until a sufficient number of the worms has been met with. My own specimens were obtained in this way, through the natives, except two younger ones, which were found under- the bark of a tree which lay half buried in the sand. The worm is of fair size, a foot or two long, by nearly half an inch wide when alive. Its colour is a dark blood-red, with a green iridescence anteriorly, the red being obscured, however, only by the black gut posteriorly. No pigmentation occurs except certain small marks on the prostomium described below. The shape of the anterior end of the body (PI. X V . fig. 7) is very characteristic of this as of several other species. The head and first few body-segments are proportionately long and round in section, forming a cylinder, but at about the fifth they become much broader and especially shorter and flatter. The broadest segment is usually about the twelfth, after which a slight decrease in breadth occurs, the rest of the worm having parallel sides and being composed of very short and flat segments. From about half an inch before the anus the segments rapidly narrow, so that the hind end is triangular (see PI. X V . figs. 7 & 9). The upwardly directed thick-lipped anus and its cirri are as figured by Gravier, but his figures of both head and anus suggest that the worm increases and decreases in breadth but slightly, and quite gradually. I find no reduced eyes on the prostomium. The pigment-marks at the bases of the tentacles and under the anterior border of the peristomial segment are shown in fig. 8, PL XV., which shows also the rings round the lower ends of the tentacles mentioned by Gravier. The tentacles are always distinctly more slender, and appear to arise nearer together than those shown by Gravier's figure. The dental apparatus is soft and brown in the two young specimens, very hard and black in the adults, a very little white matter occurring on the lower or mandibular plates. The uppermost tooth of the right great dental plate is always smaller and duller than the corresponding one on the left, and those of the right curved lateral plate are all longer than those of the left. Except near the extremities of the body, the feet present the peculiarity of being provided with no more than the stumps of their seta?. This, which would appear a mere regrettable accident |