1904.] MARIXE FAUXA OF ZANZIBAR. 305 



pair but very little shorter, wliile the outer are but half this length. 

 The median pair is inserted at the same level as the middle 

 tentacle, but at some distance laterally from it and close to the 

 outer pair, the insertion of which is more anterior. Immediately 

 beneath these last are the small but di-stinct eyes. The first 

 ring of the peristomium is of moderate length, the second very 

 short, and the nuchal cirri are small and smooth. 



The jaw-apparatus is very powerful (text-fig. 53, p. 306), con- 

 sisting of thick black plates sparingly bojxlered with white matter. 

 The end-plates of the lower jaAvsare small and but partially calca- 

 reous, being marked by dark chitinous rings, as shown in the 

 figure (text-fig. 53, B, p. 306). The upper plates are of the usual 

 form, the great dentals being broad and bearing shai-p closely- set 

 teeth. The formula is 6 — 7 : 7 + 2 — 9; the small number of teeth 

 on the second left crescentic plate is due to its being toothless 

 over the greater pai-t of its cutting-edge, a condition found less 

 j)rominently in many species, e. g. E. afra. Outside all are two 

 pai'agnaths on either side, the anterior and inner pair bearing one 

 triangular tooth each, the posterior being mere elongated chitinous 

 bands. 



The feet project but little, though the set.ie stand out pro- 

 minently. The dorsal cii'ri are fairly long, projecting well beyond 

 the seta?, except in the first three feet and those near the hind 

 end of the body. The ventral cirii are highly modified, forming- 

 secretory pads, in somewhat the same way as in Diopatra. The 

 first is thick and finger-shaped, but they rapidly become still 

 thicker until the twelfth is a conical knob as large as the setigerous 

 portion of the foot. The breadth continuing to increase dorso- 

 ventrally, at the 24th foot it is nearly three times as wide 

 as this. iSince these pads are broader than the feet, they are 

 pressed together fairly closely, forming an almost continuous band 

 down the sides of this region of the body, as shown in PI. XXL 

 fig. 4. Yentrally they end in a free flap, dorsally in a little 

 point, the remnant of the true cirrus. The figures of the feet 

 (text-fig. 54, p. 307) explain the changes of form and arrangement 

 of these organs. The lower boi-der and inner angle of the pads are 

 extremely vascular, and, at about the 120th foot, these surfaces 

 contain a- close network of blood-vessels. Posteriorly, at the point 

 where the giUs become conspicuous, the pads gradually decrease in 

 length, and when the former attain their full size about segment 

 120, the latter become rapidly smaller, and for thei-est of the body 

 beyond segment 130 are merely little conical points. One lip of 

 the seta-sac is pointed and projects a little beyond the othei', which 

 is rounded. 



The gills begin at foot 35 as a small papilla and do not become 

 at all conspicuous until about the 70th foot, where they consist of 

 two filaments somewhat larger than the dorsal cirrus. From this 

 point they increase uniformly, vintil, at the 120th foot, five long- 

 filaments are found arising from a short i-achis, a condition which 

 seems to last to near the anus (PI. XXI. figs. 1, 2, k 3). 

 Proc. Zool. Soc— 1904, Yol. I. No. XX. 20 



