IÇ2I.] Fauna of the Chilka Lake : Polychaeta. 643 



genera. The affinity between Barantolla and Mastobranchus is also indicated by the 

 crenulated skin of the anterior thoracic segments, and by the discovery in the species 

 of Mastobranchus described below of two elongate crochets in the ventral bundle of 

 the 12th segment (vide p. 646). 



A comparison of these three genera, based on a much more ample supply of 

 material, would probably lead to considerable modifications. 



The form described by Stephenson (1908, p. 39) from brackish ponds at Port 

 Canning, Lower Bengal, as Matla bengalensis may be related to one of the above 

 genera. The specimens examined were very young, i"5-4"5 mm. in length, and 

 there is little in the description to indicate what the adult would be like. 



Barantolla sculpta, sp. nov. 

 (Plate XXIX, figs. 24A-K.) 



This species is represented by a number of fragments, including the anterior ends 

 of four individuals. Unfortunately the posterior end is not present in any specimen. 



The largest fragment is 117 mm. long, composed of 135 segments. Judging 

 from the appearance of the last few segments, the missing portion of the tail is quite 

 short. The body is widest near the 4th or 5th setigerous segment (17 mm. wide), 

 and gradually tapers till near the 30th segment. It then remains fairly uniform in 

 diameter for a long distance, expanding again a little near the posterior end. The 

 length of the segments varies considerably, according to their position. In the type- 

 specimen the approximate ratio of the width to the length is in segments 1-5, 3 to 1 ; 

 segments 6-14, 4 to 1 ; segments 15-20, 3 to 1 ; segments 21-35, 2 to 1 ; segments 

 36-43, i\ to 1 ; segments 44-55, 1 to 1 ; segments 56-70, a little less than 1 to 1 ; 

 segments 71-80, 1 to 1. The segments then gradually become shorter towards the 

 tail, and the last segments are 6-8 times as wide as long. 



The head in all the specimens is contracted, and withdrawn under the peristo- 

 mium, and hence it is difficult to describe accurately. It is conical, composed of two 

 rings, a wide basal, and a narrower terminal. The latter, in its contracted condi- 

 tion, is rounded. No eyes could be seen, but behind the basal ring of the head is an 

 irregular transverse row of deeply embedded black pigment spots, which, however, 

 may have no optical function. 



The proboscis is partially extruded (fig. 24A), and this part is covered with very 

 minute papillae. 



The thorax consists of 12 segments, of which the first is achaetous. In the first 

 four segments, and to a lesser degree, in the anterior part of the 5th, the skin is dis- 

 tinctly tessellated (figs. 24A-C), but on the succeeding segments it is smooth, except 

 for ridges caused by unequal contraction of the skin. 



Segments 2-7 have capillary setae only, segments 8-12 long crochets only, and 

 the abdominal segments short crochets only. In the thoracic segments the setae are 

 near the middle of the segment, but in the abdominal segments they are near the 

 posterior end. Each of the abdominal segments is in two parts, an anterior narrow 



