ZOOLOGISCHE MEDEDEELINGEN 



UITGEGEVEN VANWEGE 



's RIJKS MUSEUM VAN NATUURLIJKE HISTORI 



ï\ 



Deel IV. 



te 

 LEIDEN 



Aflevering 3. 



IX. — ON A REMARQUABLE FRESH- WATER POLYCHAETE "NE- 

 REIS NOUHUYSI" FROM THE EAST-INDIES. 

 BY D r . R. HORST. — (WITH 1 TEXTFIGURE). 



In the year 1905 Mr. J. W. van Nouhuys presented to our Museum 

 some iVerm-specimens, collected in the Miha at thé South-coast of the 

 isle of Taliaboe, at a distance of two hours from the mouth of the river, 

 that moreover was shut off by a bank of gravel ] ). There are eleven 

 specimens, ten females and one male, all mature and in the Heteronereis- 

 form. They are characteristically marked ; in the median body-region 

 each segment shows on it dorsal side a transverse, black band, narrow 

 in the middle and growing broader laterally, on the base of the para- 

 podia. Two black spots occur on the dorsal side of each parapodium, 

 whereas the dorsal ligule is also black coloured. Ventrally the segments 

 show a similar marking ; however on the base of the parapodium there 

 occurs an oval spot, consisting of longitudinal lines and in front of it a 

 small transverse patch. The anterior ten or twelve segments have a dark 

 brown hue, with pale, oblique stripes on their lateral part; the head 

 also is dark coloured, its posterior part being somewhat paler. The largest 

 specimen has a length of 110 mm. and consists of 225 segments. The 

 head is longer than broad, elongated trapezoidal; its antennae are small, 

 whereas the palps are stout, with a small distal joint. The eyes are 

 large and nearly coalesce. The longest tentacular cirrus extends to the 

 eight segment. 



The armature of the proboscis consists on area I of a transverse, in- 

 distinctly tristichous group of about 13 to 18, distant, hook-shaped para- 

 gnaths ; on areas II and IY there occurs a curved, distichous or tristichous 

 group of acute, hook-shaped paragnaths; area III has a broad group of 

 45 to 50 paragnaths, arranged in 5 or 6 rows, the lateral ones being 



l Tijdschrift Ned. Dierk. Vereeniging (Ser. 2), Vol. IX, 1905, p. XXXVI. 



(8— VII— 19 is) 



