1921.] Fauna of the Chilka Lake : Polychaeta. 595 



setae have the same arrangement, only a single spinous heterogomph being present. 

 The remaining feet show no change, except that they decrease in size and the setae 

 become fewer in number. The anal segment is button-shaped, with two very short 

 anal cirri, only as long as the segment is wide. The anal segment and cirri are 

 possibly regenerated, as the posterior feet are quite large. 



The dorsal homogomphs are slenderer than any of the ventral setae (figs, yj and 

 7K). The falcate setae have tips of medium size with spinous edges. 



The most interesting characters of this species are those which exhibit a tendency 

 towards degradation from the normal type. These are (1) the insignificance of the 

 paragnaths on the basal segment of the proboscis. In this respect the species is 

 approaching the condition found in the sub-genus Ceratonereis, Kinberg, in which the 

 basal segment is devoid of paragnaths ; (2) the insignificance of the dorsal setigerous 

 division, indicated by the small number of dorsal setae, and the reduction in size of 

 the dorsal ligule in the anterior and posterior segments ; (3) the rarity of the spinous 

 heterogomph setae, which only occur singly in the middle and posterior segments, and 

 aie absent from the anterior segments. 



According to the classification of de Saint-Joseph (1898, p. 285), based on the 

 structure and arrangement of the paragnaths, this species belongs to the sub-genus 

 Nereis of the genus Nereis. 



A point of considerable interest, clearly established in this species at any rate, is 

 that the lobe beneath the dorsal cirrus in the ist and 2nd feet represents the median 

 ligule. A consideration of figs. 7E, 7F, and 7G leaves no room for doubt. The dorsal 

 ligule appears in the 3rd foot as a small lobe. 



Habitat. — Only a single specimen of this species was obtained, on the shore about 

 one mile from the mouth of the Chilka Lake. It was taken in September, during the 

 freshwater season, and the water was quite fresh. 



Perinereis marjorii, sp. nov. 

 (Plate XXIII, figs, ioa-g, and text-figs. 7 and 8a-c.) 



The largest of the 10 specimens of this species, from the Chilka Lake, is 61 mm. 

 long, and has 80 setigerous segments. Another is 53 mm. long, with 76 setigerous 

 segments. The body is long and slender, 2 '5- 

 2*75 mm. wide, including the parapodia at the 

 widest part. The segments are very distinct, 

 2-3 times as wide as long, and the feet are 

 comparatively short. The colour is pale pur- 

 plish brown, and is strongest on the head and 

 anterior dorsal region (fig. ioa). On the head Text-fig. 7.— Perinereis marjorii, sp. nov. 

 there are three longitudinal bands of pigment, Dorsal view of ^^^r^' showingthe 

 two of them marginal, and a shorter median 



one. Behind the latter, between the eyes, there is a V-shaped band. In the anterior 

 region of the body there are three short transverse bars on the dorsum of each seg- 

 ment, the median being a little behind the other two, leaving a colourless patch in 



