KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 63. N:0 7. 



13 



lias as a rule distinct setae. The uncini of the l st — 3 ld setigerous segments have 5—7 

 teeth, and bristles, though weak, may be found on all of them; no single uncini ob- 

 served (2—3, 2—6, 5—8 uncini respectively). The fully developed uncini have no pro- 

 jecting upper dental part; the fastening of the bristles not specially perceptible; up to 

 9 teeth. The anterior capillary setae on the 8 th — 13 th setigerous segments specially 

 fine, numerous, exceedingly finely and diffusely bordered, generally without a pencil 

 of bristles, somewhat contracted towards the base. Tubes free, rather coarse, of sand. 

 External structure. The anterior point of the head is strongly developed, 

 like the keel behind it (ef. fig. 7). The lateral borders, extending to the hindmost part 

 of the keel, are on the whole rather high, which is, however, not discovered, unless one 

 pushes them aside, for instance with a pin, in more softly preserved specimens. The 

 height of the borders decreases rather rapidly posteriorly. Between the borders and the 

 nuchal organs, which rcach practically as far back as the keel, there is on each side a 

 narrow region — somewhat wider anteriorly — representing the strongly reduced cephalic 

 plate. Ocelli are numerous round the point of the cephalic lobe; on the sides a strong 

 band of them extends a short way backwards; ef. text-figs. 1 — 2. 



Text-fig. 3. Leiochone johnstoni. — Unc-inus (second 

 from above) from the l st setigerous segment. 710: 1. 



Text-fig. 4. Leiochone johnstoni. — Uneinus from the 

 11 111 setigerous segment. 375: 1. 



Just behind the keel or behind the (when contracted ) longitudinally folded field, 

 which bounds the mouth posteriorly, is to be seen as a rule a more or less distinct limit 

 around the body (ef. fig. 7); in regenerated anterior ends it is in most cases not visible. 

 The following l st setigerous segment seems to vary not a little in length, but this is pro- 

 bably due to incomplete regeneration af ter preceding mutilation; in fig. 8 this segment is 

 comparatively short. The anterior limit of the l st setigerous segment is slightly bent 

 forward at an angle on each side in front of the parapodium. The glandless edge of the 

 2 nd — 4 th — 5 th setigerous segments shows, at least in contracted specimens and especi- 

 ally on the sides, a feeble indication, most distinct on the 3 rd setigerous segment, of a 

 c ollar. The appearance of the anterior segments is shown in other respects in fig. 8; 

 thus the 8 th setigerous segment has parapodia situated far behind, and its limit towards 

 the preceding segment is situated on the dorsal side in front of the anterior ends of the 

 elongated groups of glands that mcet here anteriorly. A glance at fig. 10 will show the 

 position of the limit here and also how it passes off straight downwards at the sides, 

 finally going round the somewhat more projecting large ventral glandular field; ef. 

 also fig. 9. 



