47 114 Proceedings of the Royal Irish Academy. 



the tail. In the anterior region the dorsal surface is natter than the ventral, 

 and the segments are very narrow. Further behind, the segments are longer 

 and the body more rounded in section. The anus is dorsal, with a ventral 

 lobe beneath. 



The head (fig. 28a) is pointed in front, and in the preserved specimens 

 neither eyes nor nuchal organs can be seen. The dorsal tentacles are on the 

 segment in front of the first setigerous segment. Each tentacle is accom- 

 panied as usual by a lateral cirrus, situated externally to it. The dorsal 

 cirri are fixed above the dorsal setae. 



Both dorsal and ventral bundles in the anterior and middle regions of the 

 body contain only capillary setae. The dorsal setae are longer than the 

 ventral setae ; but there are long and short setae in each bundle. The longest 

 setae are in the upper part of the dorsal bundles. Passing backwards these 

 dorsal setae gradually become longer, till in the 20th-30th segment they 

 attain the length of 'To-rOO mm. They then gradually decrease in length. 

 In the anterior segments there are 5-7 setae in each bundle ; in the middle 

 region, 6-8. The shorter setae in the anterior segments (fig. 28b) have a 

 cylindrical shaft and a flattened blade, with a distinct curve at the junction 

 of the shaft and the blade. 



The segment on which the crochets first appear is variable in position. In 

 the largest specimen the first ventral crochet appears in the 56th segment, 

 the first dorsal crochet in the 61st segment. 



The normal arrangement of the setae in the posterior segments is shown 

 in fig. 28 f. In the dorsal division there are two crochets in the upper part 

 of the bundle, the outer one being the largest in the whole segment (fig. 28c). 

 Then follow a smaller crochet, and 4 or 5 capillary setae, alternately long 

 and short. The ventral division usually contains 2 or 3 crochets in 

 the lower part of the foot, the lowest being also the shortest. Above the 

 crochets are 3 or 4 capillary setae closely resembling the short capillary 

 setae of the dorsal bundle (fig. 28r>, a), In the segments near the tail all the 

 capillary setae of the ventral bundle may be replaced by crochets. 



The arrangement of the crochets in the posterior segments depends on the 

 age and size of the specimens. Two individuals of 44 and 50 segments 

 respectively had crochets in the ventral bundles of the posterior 13-14 

 segments ; but the dorsal bundles consisted solely of capillary setae. Another 

 specimen, somewhat larger, had crochets in the dorsal bundles of the posterior 

 8 segments. As already stated, the largest specimen, of 84 segments, had 

 crochets dorsally in 24 segments, ventrally -in 29 segments. 



The dorsal crochets (fig. 28c) resemble the short capillary setae in shape, 

 except that the tip is curved and bifid. The uppermost crochet in the 



