's RIJKS MUSEUM VAN NATUURLIJKE HISTORIE — LEIDEN. 11 



Parahalosydna sibogae n. sp. 



Siboga-expedition, Stat. 105, north off Soeloe-island. 



At this Station a small Polynoid-worm was caught, that with regard 

 to the structure of its head and the rudimentary feature of its notopodia 

 fully agrees with Halosydna, but only possesses 15 pairs of elytra. The 

 specimen is colourless and has a length of 12 mm.; the number of its 

 segments amounts to 34. The head is provided on each side with a pair 

 of large eyes, situated next to each other, laterally in front of its poste- 

 rior margin. There are 15 pairs of elytra, covering the whole dorsum 

 and overlapping each other in the median dorsal line, they are firmly 

 attached, faintly reniform, with a smooth surface except a group of small 

 tubercles along its concave side. Their margin is without appendages and 

 the scar of attachment lies eccentrically and is associated with a nerve- 

 ganglion and numerous branching stems irradiating from it. In the para- 

 podia the dorsal lobe is rudimentary and besides the acicula only con- 

 tains three small faintly serrated bristles; the ventral setae have a smooth 

 shaft and a dilated, wedge-shaped distal part, faintly bent and serrated 

 along both edges. The dorsal cirrus is very long, about four times the 

 length of the neuropodial fascicle. This species cannot be ranged among 

 the genus Halosydna, that according to Kinoerg's diagnosis, is characte- 

 rized by an elongated body, with at least eighteen pairs of elytra, 

 „dorsum non omnino tegentia". 



Gastrolepidia Schmarda x ). 



The sternum of the segments provided with a foliaceous appendage 

 on each side. More as 21 pairs of elytra, covering the whole dorsum ; 

 from the 23 d to the 35 1 * 1 segment the elytrophore-bearing segments alter- 

 nate with two cirrophore-bearing ones, however more posteriorly the 

 arrangement becomes irregular. 



Gastrolepidia clavigera Schm. 



( — amblyphyllus Gr.) 2 ). 



Siboga-expedition, Stat. 60, Haingsisi, Samau-island, reef; Stat. 213, 

 Saleyer-anchorage ; Gaspar-strait, P. N. van Kampen, Oct. 1907. 



The prostomium, in my opinion, more agrees with that of Lepidono- 

 tus than of Harmothoe, as suggested by Darboux, for the lateral antennae 

 are inserted upon the frontal margin; however there occurs an annular 

 constriction, that makes the insertion somewhat indistinct. Schmarda 



1) Schmarda, Neue wirbellose Thiere, 1861, p. 159, PL XXXVI, tig. 315. 



2) Grube, loc. cit., p. 46, PL III, tig. 7. 



