1921.] Fauna of the Chilka Lake : Polychaeta. 647 



dorsal bundle of the 15th segment there are only crochets, 33 mm. long, in shape 

 like those of the ventral bundles. In the 20th segment the dorsal crochets are 

 '174 mm. long, the ventral crochets 108 mm. long. The nodulus is very distinct, but 

 the swelling below the neck is not so evident. In the 50th segment the dorsal crochets 

 are - I2 mm. long. In the ventral bundle there are 63 crochets, 1 mm. long 

 (fig. 25F). The nodulus is very distinct, in the middle of the shaft. 



From Garia, near Calcutta, in December 1910, were obtained two fragments of a 

 Capitellid, which may belong to the present species or to Barantolla sculpta. They are 

 both from the middle of the body, but one is evidently from a more posterior region 

 than the other. Both fragments have very powerfully developed ventro-lateral 

 muscles, which are more prominent than those of Barantolla sculpta. One fragment has 

 branchiae on each segment, behind the dorsal setae. They are very similar to those 

 of Barantolla, but rather longer, consisting of 5-7 finger-shaped lobes. The dorsal 

 tori are more elongate and the setae more numerous than those of Barantolla. In the 

 absence of any knowledge of the structure of the middle and posterior regions of 

 Mastobranchus indicus, it is not possible to assign these fragments to any species at 

 present. 



The pre sent species is assigned to the genus Mastobranchus by virtue of the 

 structure of the thorax and anterior segments of the abdomen. A knowledge of the 

 structure of the anal appendages, and branchiae (if any are present) is necessary to 

 modify or confirm this conclusion. 



In view of the great resemblance between this species and Barantolla sculpta, and 

 the presence of both forms in the brackish ponds near Barantolla, the question arises 

 whether the latter does not represent a stage in the growth of the former. All the 

 specimens of Barantolla available are immature. In the sculpture of the skin, shape 

 of the anterior end, and the form of the setae there is close resemblance. On the 

 other hand, all the specimens of Barantolla sculpta agree in having capillary setae on 

 segments 2-7, long crochets on segments 8-12, and only short crochets on the 

 anterior abdominal segments. Mastobranchus indicus has capillary setae only, on the 

 thoracic segments 2-12, with the exception of the two long crochets noted above, and 

 capillary setae in the dorsal bundles of the two anterior abdominal segments. If 

 B. sculpta is only a stage in the development of M. indicus, then the completion of 

 the metamorphosis has been postponed to an unusually late period, as the specimens 

 are at least 120 mm. long. On the whole I am inclined to regard the two forms as 

 distinct, but the question can only be definitely settled by the examination of more 

 material, at different stages of growth. 



Habitat. — A single imperfect specimen from brackish pools, salt lakes, Barantolla, 

 near Calcutta. The specific gravity of the water is very variable, but never high, 

 probably never exceeding roi5. 



