1921.] 



Fauna of the Chilka Lake : Polychaeta. 



625 



Lumbriconereis simplex, sp. nov. 

 (Plate XXVI, figs. i6a-i6m, and text-figs. i$a-b.) 



Six specimens of this species, from the Chilka Lake, all from the south-western 

 end, are available for description, all of them in a fragmentary condition, and the 

 posterior end is missing in all cases. The largest fragment is 32 mm. long, and con- 

 sists of 125 segments. It is probably half the total length, or rather more. 



The preserved animals are colourless, except for a delicate greenish iridescence. 

 There is a dark amber-coloured spot near the base of each foot, on the ventral side, 

 composed of granular pigment, like dried blood. Similar granules are scattered over 

 each foot, especially near the tip of the setigerous lobe, and just above the foot. The 

 body expands gradually up to the 15th setigerous segment, and then tapers still more 

 gradually towards the posterior end. The feet are rather prominent. The width 

 of the body at the 15th foot is 17 mm. or including the feet and cirri 27 mm. The 

 ist achaetous ring is 2% times as long as the 2nd ring. 



The head (figs. i6a, i6b) is triangular, with rounded angles, the length slightly 

 exceeding the width. No trace of eyes could 

 be found, though there is some subcutane- 

 ous pigment on the head. The mouth is 

 bounded in front by two tumid lips belong- 

 ing to the head, laterally by the first ring, 

 and in the mid-ventral region by the second 

 ring, which interrupts the first ring and pro- 

 jects forwards to the mouth. 



The ist foot (fig. i6g, and text-fig. 15a) 

 consists of a setigerous lobe composed of 

 two lamellae or fillets, and a rounded lobe 

 lying behind and beneath the fillets. Be- 

 tween the fillets lie four colourless spines, 

 bundle of two long bilimbate setae above the spines, and four similar but shorter 

 setae beneath the spines. The upper ventral seta emerges inside the inner fillet, all 

 the others between the two fillets. The succeeding feet increase in size and in the 

 number of setae. In the 10th foot (fig. i6h, and text-fig. 15Ô) the posterior lobe is 

 longer, bluntly pointed, and flattened, and the two fillets lie in front of it. There 

 are four bilimbate setae in each bundle. The succeeding feet up to the 30th show 

 little change. The base of the posterior lobe then becomes gradually fused to the 

 fillets, and the terminal portion projects backwards as a finger-shaped lobe (fig. i6k)- 

 The number of spines in the 30th -50th feet is 3, in the 100th foot there are 2. From 

 the 30th foot there are only 3 setae in each foot, one dorsal and 2 ventral. 



In the anterior segments the setae (fig. 161,) are long and tapering, with smooth 

 flattened obliquely striated blades. They are bilimbate, but the two wings are not 

 directly opposite each other, so that usually onby one is seen, The dorsal setae are longer 

 than the ventral. In the middle and posterior feet the setae (fig. i6m) have wider and 



a, 



Text-fig. 15. — Parapodial diagrams of Lum- 

 briconereis simplex, sp. nov. 



«. ist foot ; b. loth foot. 

 • = Simple capillary setae ; • = spines. 



The setae are in two groups, a dorsal 



