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Show 140 MR. CYRIL CROSSLAND ON THE [June 16, if only one specimen occurred in the collection, becomes an interesting character when it is found that it occurs in all cases, even in young specimens. Besides the characteristic long capillaries, short, remarkably broad comb-setae occur in some feet at either end of the body (PL X V . fig. 10). There are four aciculae in the anterior- feet, two or three in those of the middle region, and one posteriorly, which may or may not be accompanied by another which is almost colourless. MARPHYSA SIMPLEX, sp. nov. (Plate XV. figs. 11, 12.) Two specimens from between tide-marks, near Zanzibar Town : the larger incomplete, measuring 10 cms. by 0*45 cm., composed of 155 segments ; the smaller complete, 15 cms. long by 0*3 cm. broad. The circular section of the body is very nearly uniform throughout, and the length of the segments is greater than in the case of the preceding species, and those immediately following the head are neither longer nor narrower than the rest. The body narrows quite gradually to the anus, the opening of which is large, upwardly directed, and provided with a pair of moderately long cirri ventrally. The prostomium is bilobed, the median notch being continued dorsally as a narrow groove to its base. The tentacles are nearly twice as long as the prostomium and are delicately ringed. Their insertion, basal parts, and the position of the eye-spots are shown in fig. 11, PL X V . No considerable portion of the prostomium is hidden by the next segment. The peristomium has a total length about equal to that of the head, the segments immediately succeeding being about half as long and of the same size, or nearly so, as those composing the rest of the body. The larger pieces of the dental apparatus all show a white edging, especially prominent on the upper ends of the mandibles, which bear large plates of this calcareous matter. The great dental plates bear three teeth each in the larger specimen, four in the smaller. The teeth of the laterals are blunt, and number-four and three on the left, six on the right. The whole apparatus presents no peculiarity save the structure of the mandibles, for which see text-fig. 14, p. 142. The feet are small, and contain numerous long setae, projecting from a seta-sac, the posterior lip of which is very broad and straight-edged (text-fig. 13, p. 141). All the seta? are smooth, without toothing or borders, the capillaries being bent gently and pointed in the usual way, the articulated pieces of the compound setae being sword-like and slenderly pointed. The comb-seta? are long and slender, very finely toothed, the outer teeth on either side being considerably the longer. PL X V . fig. 12 represents a group of these seta-, showing their variation in the same foot, the distance they project from the seta-sac, &c. They are much larger than the somewhat similar ones of M. macintoshi. There are four or five aciculae in the anterior feet; three, with |