's RTJKS MUSEUM VAN NATUURLIJKE HISTORIE — LEIDEN. 19 



and afterwards found at great depth by the Blake in the West-Indian 

 Sea ') and by the Valdivia off the Somali-coast 2 ). Unfortunately both 

 worms are in a bad state of preservation and lack all the cirri as well 

 as the elytra. The thin triangular processus of the head — according to 

 Ehlers homologous with the lateral frontal corners — could be recog- 

 nized, but nothing can be said about their real nature. The flattened, 

 translucent bristles have an elongated, smooth, triangular tip, furnished 

 with a triangular ridge ; that the tip should be bifid, as suggested by 

 Mc Intosh, or provided with a pore according to Ehlers, could not be 

 confirmed. 



PoLYNOË Savigny 3 ). 



Body elongate, consisting of more than 45 segments ; elytra 1 5 pairs 

 or more, inserted on segments 2, 4, 5, 7 . . . . 23, 26, 29 etc., restricted 

 to the anterior region of the body (Hemilepidia Schm.) or not (Holole- 

 pidetta Willey). Notopodial bristles more slender than neuropodial ones. 



Polynoë (Hemilepidia) Versluysi n. sp. 



Siboga-expedition, Stat. 251, south off Koer-island; Stat. 253, south 

 off Taam-island. 



Commensal on Primnoidae (Thouarella hilgendorft Stud.) 4 ) Yersluys 

 met with a Polynoid-worm, that is characterized by its long dorsal cirri 

 and its elytra, that are restricted to the anterior half of the body; they 

 live in ducts, formed by the short branches of the Alcyonarian, that are 

 placed close together, while their tips are inclining towards each other, 

 thus forming a kind of avenue. The head is separated by a median dor- 

 sal groove in two halves ; between them the basal part of a tentacle arises, 

 that bears a long and slender distal joint, reaching till on the 5 th seg- 

 ment. There are two pairs of large eyes, the posterior of which are 

 situated in front of the posterior margin of the head, whereas the ante- 

 rior pair occurs on the lateral prominences. 15 pairs of elytra are restric- 

 ted to the anterior region of the body ; each of them is rounded rectan- 

 gular, with the scar of attachment situated eccentrically. Their surface is 

 densely beset with small, obtuse, spinous tubercles and some small cy- 

 lyndrical papillae along their margin. No dorsal tubercles are present. 



1) Augener, West-lndische Polychaeten, p. 123. 



2) Bodensàssigen Annelideu der deutsch. Tiefsee-Exp. p. 40, PI. II, figs. 10, 11, PI. Ill, 

 figs. 1 — 5. 



3) Système des Annelides, p. 20. 



4) Siboga-espeditie, Vol. XIII, die Gorgoniden*. Primnoidae, p. 25. 



