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



long, had 120 setigerous segments. Another fragment, full of sperm, was 16 mm. long, 

 with 65 setigerous segments, and was rather stouter than the other immature speci- 

 mens. A complete individual 19 mm. long had 105 setigerous segments. 



The head (fig. ia) bears in front two flattened palps, fused in the median line 

 where they are very thin and transparent. The front margin is concave. Each palp 

 has a small terminal joint. The postero-lateral angles, where the head is widest, are 

 rounded and indented. The posterior border is concealed beneath the very thin pro- 

 jecting margin of the peristomium. There are three tentacles, the median, which is 

 nearly twice as long as the laterals, being slightly in front of them. The lateral ten- 

 tacles project a little beyond the palps. 



As in A . robusta, Ehlers, the entrance to the pharynx is guarded by large pear- 

 shaped papillae, 14 in number. In A. robusta there are 16 of them. When the pro- 

 boscis is fully extruded, the mouth is a vertical slit, but when retracted the mouth is 

 large and gaping, bounded behind by the much folded lower lip, in front and at the 

 sides by the folded and flattened palps. No jaws are present. In the dorsal median 

 line the projecting collar of the peristomium is fused with the head, and only sepa- 

 rated from it by a faint groove. At the sides of the head, and in front of the tenta- 

 cular cirri, the peristomium has two forwardly projecting rounded lobes. There are 

 two pairs of tentacular cirri placed near the front of the peristomium. The dorsal 

 pair are about one quarter longer than the ventral pair, and all have filiform tips and 

 swollen bases. Neither setigerous lobes, setae, nor spines are present. 



The succeeding segment bears the first pair of parapodia. They are distinguished 

 from the remaining feet by the very long and tapering dorsal cirri (fig. ib), which 

 doubtless function as tentacular cirri, and are as long as the median tentacle. The 

 ventral cirrus is clavate, less than one- third as long as the dorsal cirrus. The seti- 

 gerous lobe is pointed at the tip, where the spine terminates. Two rows of simple 

 capillary setae lie obliquely above and below the spine. The anterior setae in each 

 row are short, strongly curved, and coarsely serrated (fig. if). The posterior setae 

 are three times as long, gently curved and very slender, the upper edge being smooth 

 and very thin. There is a gradual transition from one extreme to the other, and the 

 two groups, above and below the spine, are similar. The dorsal division of the foot 

 is represented by a single short and very slender spine, which pierces the base of the 

 dorsal cirrus. 



The second foot (fig. ic) is very minute. The clavate dorsal cirrus projects be- 

 yond the conical setigerous lobe, and there is no ventral cirrus, a rather remarkable 

 feature. The dorsal spine is very small. In each group of setae there are six or 

 seven with coarse teeth, two with short teeth, and three or four smooth setae. The 

 next few feet increase till the normal size is attained. The setae increase in numbers, 

 and there are very few intermediate between the coarsely serrate and the smooth 

 forms, except as regards length. One of these intermediate forms is shown in fig. iG. 

 Some of the long posterior setae show minute serrations, and this is probably the 

 original condition, the smooth ones having lost their teeth by abrasion, as the edge 

 of the seta on which they occur is very thin. In the 4th foot the dorsal spine is 



