634 Memoirs of the Indian Museum. [Vot. V, 



again slightly, the blade, instead of tapering very gradually, narrowing abruptly 

 near the tip (fig. 19G). The branchiae have gradually increased, and the 30th foot 

 may be taken as typical of the median and posterior regions of the body (fig. 19E, 

 and text-fig. 18&), 



The branchiae are large and tapering and covered with cilia. They lie close to- 

 gether near the median dorsal line. The dorsal cirrus is fusiform, and a thin fillet at its 

 base lies behind the dorsal setae. The ventral setigerous lobe is also constricted at 

 the base and bilobate at the tip. The ventral setae emerge in a bunch just in front 

 of the bifid tip, and are guarded by a low anterior fillet. Beneath the ventral divi- 

 sion is the delicate pocket-shaped membrane, from which the specific name is derived. 

 It is attached by its anterior edge in a line with the setigerous lobes, and its shorter 

 posterior margin is thus behind the foot. The setae are almost equally long in both 

 divisions. Very little change takes place in the succeeding feet. In the 70th foot 

 the dorsal cirrus is half as long again as the branchia, which is very short and stout, 

 but in the 150th foot the two are equal in length. As only a single specimen was 

 available it is impossible to say whether these variations have any significance. 

 The posterior 10 pairs of feet decrease rapidly in size. The anal segment is large 

 and cylindrical and the anus is terminal. There are two very slender dorso-lateral 

 anal cirri. 



This species differs from S. armiger (Müller) in many respects. In the latter 

 species the pockets below the feet are absent. The position of the first branchia 

 differs, as does the shape and arrangement of the anterior feet, the shape of the 

 setae, etc. 



S. kerguelensis, Mcintosh, is easily distinguished from the present species by the 

 shape of the setae, the position of the first branchiae, etc. 



Habitat. — A single specimen was found in the outer channel at Manikpatna 

 Island, during the salt-water season, when the specific gravity of the water was about 

 1-0264. It probably lives there throughout the year, though this remains doubtful, 

 in the absence of material collected during the freshwater season. 



Family SPIONIDAE. 

 Polydora hornelli t Willey. 

 (Plate XXVIII, figs. 2IA-D.) 

 1905. Polydora homelli, Willey. p. 286. 

 A single specimen, the posterior part of which is missing, was found in an oyster 

 shell at Manikpatna, Chilka Lake. It exhibits no obvious characters by which it can 

 be distinguished from the P. homelli described by Willey {torn, cit.), who obtained 

 his specimens from pearl oysters in the Gulf of Manaar, Ceylon. Unfortunately 

 Willey' s description is rather brief, and is illustrated only by a single figure showing 

 one of the modified setae of the 5th segment. He gives no account of the structure 

 of the posterior region, so important in diagnosing the species of this genus, and the 

 absence of the tail in the Chilka specimen prevents me from completing his account. 



