246 ZOOLOGISCHE MEDEDEELINGEN — DEEL IV. 



XV. - ON A SPECIES OF LYCASTIS AND THREE ABERRANT 

 FORMS OF NEREIDAE FROM THE DUTCH EAST INDIES. 

 BY Dr. R. HORST, 



Lycastis meraukensis n. sp. 



Dr. J. W. R. Koch, member of the New-Gruinea expedition of the 

 Kon. Nederl. Aardrijkskundig Genootschap in 1904, found at Merauke 

 in decayed wood of the Sago-palm 9 specimens of this worm, viz. 2 large 

 ones, one of which is incomplete and 7 smaller ones. Unfortunately it is 

 not mentioned whether the tree was met with in fresh or brackish water 

 of the river or in salt water at the sea-shore. The dorsal side of some 

 of the worms is dark flesh-coloured, whereas a red brown ring occurs 

 around the anal segment. The largest specimen measures about 150 mm. 

 in length and has a breadth of 7 mm. in the median body-region (without 

 the parapodia); the number of its segments amounts to 170. One of the 

 smaller specimens has a length of 60 mm. and consists of about 150 seg- 

 ments. The head is more broad' than long, rounded trapezoidal, provided 

 with a longitudinal median groove. The eyes are situated laterally, in 

 front of the posterior margin of the head; the external of each pair is 

 the largest and it is placed somewhat more anteriorly than the internal. 

 The antennae are short, conical; the palps consist of a stout basal part 

 and a small, papilliform, distal joint. The maxillae are short and stout, 

 provided with six teeth. The longitudinal diameter of the buccal segment 

 is as long as that of the succeeding segment or somewhat shorter. The 

 longest tentacular cirrus reaches to the 2nd or 3rd segment. 



The Merauke-worm is not slender, rather coarse and it belongs to 

 that group of Lycastis-sipecies, which have the dorsal cirrus enlarged and 

 flattened, to form a leaf-like structure; as the cirri of the succeeding 

 segments are overlaying each other, the worm somewhat resembles a 

 Phyllodocid. In the small specimens the dorsal cirrus is slender and pointed, 

 extending in the median and posterior segments a good deal beyond the 

 neuropodial bristle-fascicle; they lack the notopodial bristles, the acicula 

 only being present. In the larger specimens however the dorsal cirrus 

 is broad, triangular, extending nearly to the distal extremity of the 

 neuropodial bristle-fascicle; though their notopodium is coalesced 'with 

 the neuropodium it contains besides a stout, black acicula a fascicle of 

 eight to ten slender, faintly heterogomph setose bristles. The parapodia 

 of the posterior body-region lack these last-named bristles. The. neuropo- 

 dium is cylindrical with a notch in the middle of it edge, from which 



