584 Memoirs of the Indian Museum. [Vol. V, 



terminal pieces are short, and they taper rapidly to a fine point (fig. 3J). The 

 terminal pieces of the ventral setae are 2-4 times as long, and taper very gradually 

 to the" tip. The space between the ventral ligule and the ventral cirrus has greatly 

 increased. 



The 70th foot (fig. 3G) is smaller, and the setigerous lobes and fillets are reduced 

 and flattened. The setae in the dorsal division have stouter shafts than those in 

 the ventral division. In the posterior feet (fig. 3H) the two setigerous divisions 

 are more widely separated. In the dorsal setigerous lobe the upper lobe is reduced 

 to a small papilla, but the lower lobe has relatively increased. The ventral fillet is 

 still very obvious, giving a bifid appearance to the ventral division. The dorsal 

 setae have longer tips, which taper more gradually than those in the middle region 

 of the body. 



The anal segment (fig. 3B) is bright red in colour. It is button-shaped, and 

 the anus is round and terminal. The ventral anal cirri are short and slender. 



The dorsal setae are all pure homogomphs, but some of the ventral setae show 

 a tendency towards the hemigomph condition, the enlarged cup-shaped tip of the shaft 

 having a process on one side, of variable size. 



This species is very closely related to the T. bogoyawlenskyi described by 

 Fauvel (1911, p. 376) from a single specimen collected in the Persian Gulf, 

 for which he created the genus Tylonereis. This genus is characterised by the 

 presence of soft papillae only on the proboscis, by the structure of the dorsal 

 setigerous division of the feet, and by having setae of one type only. T. 

 bogoyawlenskyi differs from the present species chiefly by the trilobed condition of 

 the ventral setigerous lobe in the anterior feet. Other minor characters 

 distinguishing the present species are the shape of the head and tentacular cirri, the 

 red anal segment, the shape of the setae, and the proportions of the various parts of 

 the feet. The change in the condition of the dorsal setigerous lobe apparently occurs 

 in a more anterior position in T. fauveli. According to Fauvel there is no difference 

 between the dorsal and ventral setae. A noteworthy character of the two species of 

 Tylonereis is the apparent absence of the median ligule of the foot. Possibly, how- 

 ever, it may be represented in the anterior segments by the retractile lobe, and in 

 the posterior segments by the lower lobe of the dorsal setigerous division. 



Habitat. — This species was taken on two occasions, in the Chilka L,ake, both times 

 in the outer channel. It was taken in September, when the water was quite fresh, 

 and in March, when the specific gravity was 1/0265, showing that it can withstand 

 the full rigours of the violent seasonal alternation of conditions in the outer channel. 



Nereis (Nereis) chilkaënsis, sp. nov. 



(Plate XXII, figs.- 8a-r, and text-figs, ^a-c.) 



This species was found in great abundance in the southern half of the Chilka 

 Lake. It is evidently quite at home there, for both immature and heteronereid stages 

 were found. 



