1921.] Fauna of the Chilka Lake : Polychaeta. 615 



The 150th foot (fig. 14G, and text-fig. I2<?) is mammillate, with a tapering dorsal 

 cirrus. The posterior lobe is small, and is almost completely surrounded by the 

 inner fillet. There are 12 brush setae and 4 capillaries in the dorsal group. In the 

 ventral group there are 3 stout capillaries with acutely tapering tips, and 2 very 

 thick bifid hooks. In the latter (fig. 14p) the lower tooth is now much longer than 

 the upper one. Towards the posterior end of the body the foot becomes smaller and 

 more elongate, the setae fewer in number, and only one ventral hook occurs. The 

 spines which pierce the dorsal cirrus are fewer in number and much finer and shorter. 

 In none of the large specimens is the anal end complete. 



The dorsal capillary setae show certain interesting changes as one passes from 

 the anterior end backwards. In the 4 anterior feet they are devoid of wings. A 

 certain number of feet follow in which the setae have narrow wings and smooth edges 

 (fig. 14H). In the middle and posterior feet they are as shown in figs. 14K, 141,. The 

 wings are not quite opposite each other, so that in side view only one is seen. The 

 proximal part of the wing expands suddenly, and the margin is finely but distinctly 

 toothed. In setae from the posterior feet this serrate part is more elongate than in 

 those from the mid-body. The ventral capillary setae also show changes. The 

 blade becomes wider and shorter and the abruptly filiform tip more obvious in the 

 posterior feet. The tapering part of the seta is minutely spinous. The acicula are 

 not wider than the ventral capillaries, and approach them in shape, the filiform tip 

 being very notable. The brush setae are not flat, but have the edges curved towards 

 each other. 



The smaller specimens differ in several respects from the above description. 

 The most obvious difference is in the branchiae. Fig. 14R shows the 10th foot of 

 one of these specimens. The branchia is many times longer than the dorsal cirrus, 

 which is only about twice as long as the posterior lobe. The filaments are longer, and 

 not so crowded on the stem. In a few specimens the ist branchia is on the 4th foot, 

 but in the majority it is on the 5th. The anterior branchiae are relatively much 

 longer than in the large specimens. The last branchia occurs on the 37th-39th foot, 

 and there are very few with only a single filament. In some specimens the 

 filaments are long, and loosely arranged, but in others they are bushy, as in the large 

 specimens. In the smallest of the large sp ecimens the ist branchia is on the 5th 

 foot, and the filaments are long and loosely arranged, but the stem is only as long as 

 the dorsal cirrus. In the small specimens the serrate part of the dorsal capillary 

 setae is more elongate and not so wide as in the large specimens. The peristomium 

 does not project over the posterior margin of the head. 



Only one of the small specimens is complete. It measures 64 mm. in length, and 

 has 150 segments. The rest are incomplete, some larger than this, and some 

 smaller. The anal segment is button-shaped, and bears 4 ventral cirri, the upper 

 pair being 4 times as long as the lower pair, and equal in length to the last 6 seg- 

 ments. In one of these small specimens, one of the ventral .hooks of the 3rd foot has 

 2 teeth beneath the main fang, but this is exceptional. In the structure of the 

 head, jaws and tubes, the two forms agree closely. If these specimens had come from 



