1921.] Fauna of the Chilka Lake : Polychaeta. 635 



The single incomplete individual is 31 mm. long, consisting of 92 segments. After 

 preservation in alcohol, it is quite colourless. 



The head (fig. 21A) corresponds fairly well with the description given by Willey. 

 The prostomium is slightly indented in front. Between the bases of the tentacles 

 there is an oval area of the prostomium, separated by grooves, which seems to corre- 

 spond to the ' ocular area ' of Willey. The prostomial ridge, or caruncle, runs back 

 to the end of the 3rd setigerous segment. No eyes were observed. The tentacles are 

 stout, long and firmly attached. 



The ist foot has a bundle of ventral capillary setae, with a cirrus (the ventral 

 lamella) behind them. There are no dorsal setae, but just outside the base of the 

 tentacles on each side is a small conical lobe, representing the dorsal lamella. 



The dorsal bundles of the succeeding feet have two rows of setae, the anterior row 

 consisting of short setae, the posterior row of long setae. 



The 5th setigerous segment (fig. 21B) bears the modified setae. In the middle 

 of the lateral region is a curved row of 8 or 9 stout hooks, alternating with as many 

 pointed setae. At the anterior end of the row is a bunch of capillary setae, the dorsal 

 superior setae. According to Willey (torn, cit.) these setae are absent in his speci- 

 mens. There is no trace of dorsal or ventral lamellae. Beneath the middle of the 

 modified setae is a tuft of capillary setae, representing the ventral bundle. 



The tips of the hooks differ according to their position in the row. The oldest 

 hooks, at the anterior end of the row, are worn at the tip (fig. 21c, a, a 1 ), which is 

 spoon-shaped, with a distinct excavation, and a neck below. The unworn posterior 

 hooks (fig. 21C, b) have a closely applied tooth, which occupies the concavity of the 

 tip. The latter type is figured by Willey (1905, PI. V, fig. 117). The capillary setae 

 which alternate with the hooks, and which represent the anterior row of dorsal inferior 

 setae, have rather short flattened blades and slender tips, and the dorsal superior 

 setae resemble them. 



The branchiae and ventral crochets appear on the 7th setigerous segment. The 

 branchiae continue to the end of the imperfect worm (the 92nd setigerous segment 

 at least). The crochets (fig. 21D) have a distinct constriction beneath the neck. The 

 main tooth is long and pointed, making an angle somewhat less than 90 with the shaft. 

 There is a simple tooth on the. crest, making an angle of 45 with the main tooth. 



This specimen is very close to the P. hornelli of Willey. The chief differences are (1) 

 the caruncle extends over the 3 anterior setigerous segments, whereas Willey gives 2 

 segments for his specimens; (2) the dorsal superior group of setae of the 5 th setigerous 

 segment is present in the Chilka specimen, absent in the Ceylon specimens. It is 

 possible that a closer examination of the Ceylon specimens would show other differ- 

 ences, which would necessitate the creation of a new species for the Chilka form, but 

 meanwhile it may be regarded as a variety of Willey' s species. There is no doubt 

 but that this species is distinct from P. ciliata (Johnston). 



Habitat. — In crevices of oyster shells, Manikpatna, Chilka I^ake. The specimen 

 was collected in September, when the water was quite fresh. From the nature of its 

 habitat it is highly probable that it survives through the salt-water season. 



