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Show 144 ON THE MARINE FAUNA OF ZANZIBAR. [June 16, All authors agree as to the characteristic form of the eyes. As noticed by Grube and seen in the present collection, they vary in breadth from narrow crescents to kidney- or bean-shape, yet never becoming merely oval. The lower or mandibular jaw-plates are most characteristic in constitution and form, being usually calcareous with special plates of brown or black horny material. Marenzeller's figure is the only adequate representation of a very beautiful structure. The number of teeth on the left great dental plate varies from three to five, though usually it bears, as does always the right, four teeth. The curved laterals are exceptionally variable, as shown by the formulae 3 + 5 - 5 ; 5 + 1 - 5 ; 3 + 1 - 5 ; 3 + 3 - 3; 4 + 5-3. All authors agree in making the dorsal and ventral cirri much longer than those figured by Gravier. In all the specimens I have examined, their tips extend as far as do the lips of the seta-sac, or in anterior feet a little further. The articulated pieces of the compound setae are not always the shape of an equilateral triangle, being usually somewhat longer. Their shafts are bent and broadened distally, and the striation and the toothing at the point opposite the articulation (mentioned by Gravier, but best seen in Marenzeller's figure), like the bordering of the capillary seta?, are not always distinct. The acicular setae always bear two distinct hooks, when not damaged by wear, as sometimes happens, but only in a few cases does their covering or winging remain. EXPLANATION OP THE PLATES. PLATE XIV. Fig. 1. Diopatra neapolitana (p. 132). Ventral view of the head after removal of the jaw-apparatus. ces., (.esophagus ; b.tc, body-wall; a, lip of jaw-sac ; b, lip of oesophagus with its tubercles. 2. Onuphis holobranchiata (p. 135). Head and anterior end, showing the characteristic pigmentation. 3. 3Iarphysa macintoshi, sp. nov. (p. 137). Head and anterior end. 4. 25th foot of the same. 5. Compound seta? from 25th foot. Comb-seta? from the 100th foot. The whole free length of these is represented. 6. 160th foot of the same. PLATE XV. Fig. 7. Anterior end of Marphysa mossambica (p. 139), showing the proportions of the body in spirit-specimens. 8. Ditto. The front edge of the peristomium is cut away to show the pigment-marks on the tentacles and prostomium. 9. Hind end, anus and its cirri. 10. Group of comb-setie from one of the posterior feet, showing the extent of their projection from the seta-sac. 11. Marphysa simplex, sp. nov. (p. 140). The ringing of the tentacles is rather too strongly emphasised in this figure. 12. Group of comb-seta? from the 60th foot. 13. Marphysa furcellata, sp. nov. (p. 141). Head and anterior end. 14. Tip of seta-sac of 120th foot, shewing the short strong combs characteristic of the species. |