Clare Island Survey — Arcluannelida and Pohjchacta. 47 109 



(fig. 26c). On the lower margin of the dorsal and the upper margin of the 

 ventral divisions are 2 or 3 very slender, short, smooth setae. Curved hooks 

 appear in the ventral division of the 21st setigerous segment, and in the 

 dorsal division of the 35th-41st segment. The ventral hooks are slightly 

 thicker, shorter, and more strongly curved than the dorsal hooks (fig. 26d). 

 In the 26th foot there are 9-11 capillary setae in the dorsal division, 3 hooks 

 and 4 capillary setae in the ventral division. 



In the 75th foot there are 3-4 capillary setae and 2-3 hooks in the dorsal 

 division, 3 capillary setae and 3 hooks in the ventral division. In the 

 posterior feet there are 1-2 capillary setae and 2-3 hooks in each division of 

 the foot. The dorsal capillary setae are longer than those in the ventral 

 division. The difference in size between the dorsal and ventral hooks in the 

 posterior segments is not so great as in C. tentamlatus. 



The other specimens of this species show very little variation from the 

 above description. In one specimen, obtained in Laminaria roots in Dublin 

 Bay, the dorsal tentacles encroach on the lateral areas of the third setigerous 

 segment. A. specimen from Lough Swilly has a small dorsal bundle of setae 

 on the third post-oral segment. 



Mature specimens were found in August. 



This species differs from G. tcntaculatus in the following respects : — 

 (1) Smaller size and smaller number of segments ; (2) smaller number of 

 dorsal tentacles (in C. tcntaculatus the latter form an almost continuous 

 band across the segment) ; (3) the dorsal tentacles are on the 4th setigerous 

 segment, those of C. tcntaculatus being on the 6th or 7th ; (4) the distance 

 between the cirri and the dorsal setae is greater in 0. norvegicus than in 

 C. tcntaculatus ; (5) the hooks appear in a more anterior region than in 



C. tcntaculatus. 



The relations with C. JttigerusD. Chiaje are somewhat closer. The chief 

 differences are : — (1) and (2) as above; (3) the dorsal tentacles in C. Jiligcrus 

 are on the 5th-7th setigerous segment ; (4) the distance between the cirrus 

 and the dorsal setae in C. jiligcrus exceeds that between the dorsal and ventral 

 setae, reversing the ratio found in C. norvegicus. 



The chief reasons in favour of regarding these Irish specimens as belonging 

 to the same species as that described by Eathke are : — (1) the occurrence of 

 the dorsal tentacles on the 4th setigerous segment ; (2) the number of tentacles 

 is the same in both forms ; (3) the number and arrangement of the capillary 

 setae and hooks in the posterior segments and the relative position of the 

 dorsal cirri are in close agreement. 



This species seems to be the same as that recently mentioned by 

 Mcintosh (1911, p. 154) as "A form approaching Cirralulus jiligcrus 



D. Chiaje, from Malahide, Co. Dublin." 



