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Show 1903.] MARINE FAUNA OF ZANZIBAR. 133 supplement the earlier description and in a few details to correct it. As, however, a complete description, by Professor Mcintosh, of specimens obtained by the ' Porcupine' * has recently appeared, there is no need for m e to do more than summarise the most definite points. If the proportionate sizes of gills and tentacles were ever approximately constant, surely they would be so in this species, in which their large size is so characteristic. I find, however, that the first gill, which is usually on the fourth foot, is often on the fifth. (Claparede and Grube give the fifth as the first gill-bearing foot.) The ringing of the gill-bases, upon which stress is laid in Grube's tabulation of the species, m ay be quite obvious or only to be made out by very careful examination. The anterior feet are ringed very faintly. The last gill-bearing segment may be any one between the fiftieth and sixtieth, and in one case it was the fiftieth on the right side, the fifty-fifth on the left. The gills, when laid forward, may extend either to the middle of the first setigerous segment or beyond the front of the prostomium. The buccal and first three setigerous segments are of about the same length, but those succeeding rapidly shorten, so that numbers four to eight or twelve are the shortest in the body. The palps are very large, together forming an area greater- than that of the prostomium itself. Between them is a deep and narrow groove bounded anteriorly by a tubercle, which leads back a little dorsally to the oesophagus, separation of which from the jaw-apparatus is effected by a pair of lips bearing large tubercles (PI. X I V . fig. 1). I do not find in either set of specimens any seta? corresponding to Claparede's fig. 4 D, pi. vi. of the ' Annelides du G. de Naples.' The compound seta? (" soies incompletement composees ") of the first three feet have invariably two hooks, which are quite distinct. In the Naples specimens the comb-set?e have few teeth, and these are remarkably broad and flat; the capillary seta?, like the aciculse, are gently bent near their ends, a fact which led Claparede to describe them as being bordered or ending in a lance-head. This is not the case, though their sides are toothed, the teeth usually being fine but sometimes large and coarse. The Zanzibar specimens agree with those mentioned above except that the teeth of the combs are very fine and numerous, and that the distal filaments of the gills are almost as long as the proximal. In the Naples specimens the shape of the gill agrees with Claparede's figure in the shortness of the distal filaments. These differences, though constant, do not warrant the creation of a specially named variety. At Prof. Mcintosh's suggestion I append an account of further observations on the variation of the special anterior feet, to which importance has been attached by systematists. Prof. Mcintosh f * '-Notes from the Gattv Marine Laboratory," Ann. & Mag. Nat. Hist. (ser. 7) vol. xii. p. 128 (1903). f M y thanks are due to Prof. Mcintosh for showing m e his preparations and for an opportunity of discussing them with him. |
