47 126 Proceedings of the Royal Irish Academy. 



each segment. The branchiae on the second segment are somewhat larger 

 than those on the third segment. 



Capillary setae commence on the third segment, as in the genus 

 Thelepus, but they are only present on fifteen segments On the 3rd and 

 ■±th segments a conspicuous row of glands runs round the segment in a line 

 with the setae (figs. 30a, 30b). In each of the dorsal bundles the setae are 

 in two rows. The posterior row consists of long slender setae (fig. 30c), 

 tapering to a fine point, with a smooth edge and narrow unequal wings. The 

 anterior row consists of shorter setae, with narrower wings, and with more 

 abruptly tapered tips (fig. 30n). 



The ventral rows of uncini only commence on the 11th segment (9th 

 setigerous segment). In the genus Thelepus they commence on the 5th 

 segment. On the 9th setigerous segment there are 9 uncini, on the 10th 

 there are 20, on the ISth 93, and on the 26th there are 86. They are 

 arranged side by side in a single row, with no alternation. In the posterior 

 segments they are moved by long slender chitinous tendons (' soies de 

 soutien'). In side view (fig. 30e, a), each uncinus shows two teeth above the 

 main tooth. The base is rounded, with a sharp spinous muscle attachment 

 in front, and a blunt one on the posterior border. In surface view (fig. 30b, b) 

 the crest shows a single row of seven slender teeth above the main tooth. The 

 uncini of the posterior segments are slightly larger than those of the anterior 

 segments. 



These uncini differ considerably in shape from those so characteristic of 

 the genus Thelepus. The rounded button-shaped knob on the base of the 

 uncini of Thelepus is represented in the present species by a sharp spine, as 

 in most genera of the Terebellidae. Moreover in Thelepus there are usually 

 two or three rows of teeth on the crest of the uncini, as against a single 

 row in Thelepides. 



In these circumstances I propose a new genus for this form, which may 

 be provisionally defined as follows : — 



Thelepides gen. nov. 



Forms agreeing with Thelepus in liaving (1) setae on tlie third segment ; 

 (2) filiform unbranched gills ; (3) uncini in a single row. They differ from 

 Thelepus in having (1) capillary setae on 15 segments only ; (2) uncini with a 

 single row of teeth on the crest, without the characteristic knob on the base. The 

 uncini commence on tlie eleventh segment, those of Thelepus on the fifth. 



Habitat— Clew Bay— Dredged in 15 fms., 9 miles E.S.E. of Clare I. 

 lighthouse, on stony ground. 



