1921.] Fauna of the Chilka Lake ; Polychaeta. 617 



with their tubes, near Ganta Sila, Rambha Bay. This worm lives at the edge of the 

 lake in muddy sand or sand}^ mud, at a depth of about two feet below the surface of 

 the bottom. When the water is high, its burrows are covered by 5 or 6 feet of water, 

 but the fore part of the tube is exposed as the level sinks in the dry weather. The 

 upper part of the tube is shaped like the ventilation funnel on a steamer, and in 

 places where suitable molluscs occur, the worm fixes a single white shell on the top of 

 the funnel, rendering the structure very conspicuous. The specimens of the animal 

 are very difficult to obtain, and so far as I remember, we only succeeded in digging 

 them out on one occasion, on which the tops of the tubes were exposed." 



The tubes are large and thick- walled, formed of mud and sand on a membran- 

 ous basis. These specimens were taken in water of specific gravity about roll. 

 Empty tubes of similar form, though smaller, were taken in 10-12 feet of water, off 

 Nalbano. 



The small specimens were taken at nine stations, usually in the dredge, in as 

 much as 15 feet of water. Seven of these stations were south of a line joining 

 Patsahanipur with Nalbano, one station was a little north of this line, and the remain- 

 ing station was in the north-west corner of the lake, off Kalupara Ghat. The 

 water was always of low salinity, the specific gravity ranging from rooo-roio. 

 Four stations were worked during the salt-water season, and five during the fresh- 

 water season. 



Marphysa gravelyi, sp. nov. 



(Plates XXIV, figs. 13A-G, and XXV, 13H-L, and text-figs. 13«-^.) 



Twenty-seven specimens of this species, all from the Chilka Lake, are available 

 for study. They .are of various sizes, but fall roughly into two groups, with probably 

 an age difference of a year between them. A specimen from each of these two groups 

 was examined, and there is no doubt but that they belong to the same species, the dis- 

 tinctions noted being all explicable by the difference in size and age. 



The larger (type) specimen is 172 mm. long, composed of 360 segments. The 

 body is cylindrical so far back as the 5th segment. It then becomes flattened dorso- 

 ventrally. The skin is iridescent, and the dorsum shows faint white spots in front, 

 which are probably much more distinct in living specimens. 



The head (fig. 13A) is rounded at the sides, deeply indented in front. The inden- 

 tation is continued as a groove, running dorsally to the base of the median tentacle, 

 ventrally to the mouth. The median tentacle is slightly longer than, and the ex- 

 ternal tentacle slightly shorter than, the other two. Two small black eyes lie between 

 the bases of the lateral tentacles, hidden by the projecting collar of the peristomiurn 

 (fig. 13 a is from a small specimen). The head is followed by two achaetous segments, 

 of which the first — the peristomiurn — is about three times as long as the next and 

 succeeding segments. 



The anal segment (fig. 13B) is button-shaped, with a crenate margin. On the 

 ventral border are two long cylindrical anal cirri, and beneath these another pair of 

 very small stumpy cirri. 



