's RIJKS MUSEUM VAN NATUURLIJKE HISTORIE — LEIDEN. 249 



parapodia the ventral cirrus is gibbous, whereas in the anterior 7 para- 

 podia the dorsal cirrus is swollen in front of the short filiform tip. The 

 parapodia of the epigamous region show the usual lamellae at the ventral 

 lobe and at the base of the dorsal and ventral cirrus; moreover the 

 ventral ligule has its distal extremity dilated into a lamella. The dorsal 

 cirrus is provided along its ventral border with a dozen of rather large pa- 

 pillae. The terminal pieces of the swimming bristles have their broad 

 distal part terminated by an apex. The epigamous change of the para- 

 podia commences with the 16th segment; in the posterior half of this 

 body-region the segments are provided with a conical papilla in the 

 median, dorsal line. 



The head is provided with two pairs of large eyes, that are coalesced 

 on each side. The antennae are shorter than the longitudinal diameter 

 of the head and are as long as the palpi. The longest tentacular cirri 

 reach only to the 3rd segment. 



The armature of the proboscis consists of: 

 I = a single hook-like bent paragnathe. 

 II = a crescent, indistinctly distichous group of about 20 paragnaths. 



IV = a triangular group of about 25 paragnaths, the anterior ones 

 inconspicuous. 



Ill = a transverse, crescent group of 3 rows of paragnaths (9 + 8 + 7), 

 the anterior ones very tiny. 



Y = 0. 



VI = a small group, consisting of a large paragnath and some smaller 

 ones. 



YII — VIII = an indistinctly distichous belt of about 18 paragnaths. 



The specimen has a length of about 15 mm. 



With regard to the uniformity of structure of the parapodium, pre- 

 sented by nearly all the Nereidae, this species shows a remarquable 

 exception. 



Ceratonereis tripartita n. sp. 



Siboga-expedition, Stat. 40, anchorage off Poeloe Kawassang, Paternoster 

 islands. 



Among the Nereids, captured with the townet at the above-named 

 station, there are several Heteronereis-STpecimens, as shown by the arma- 

 ture of the dissected proboscis, belonging to the subgenus Ceratonereis. 

 They measure about 13 mm. in length and have a peculiar appearance, 

 because the body consists of three regions clearly distinguished from 

 each other, viz.: 1° an anterior region, about 3 mm. long, consisting of 

 the head and 25 segments, in which the parapodia are not modified ; 



