Clare Island Survey — Archiannelida and Polychaeta. Q!°t 49 



Castalia fusca var. hibernica var. nov. 

 PL V, fig. 8. 



In a remarkable haul of the dredge in Clew Bay (Station W. 84), in 

 24 fms., a number of specimens were secured which, whilst agreeing generally 

 with Castalia fusca, yet show a number of definite differences. Of these the 

 chief are: (1) the eyes are red, those of C. fusca being black; (2) the very 

 characteristic coarse teeth on the terminal pieces of the setae of C. fusca are 

 not found in this form ; (3) the setae are shorter and thicker, the terminal 

 pieces tend to be bifid at the tip, especially in the dorsal part of the foot, and 

 in the posterior segments. Setae with simple and bifid points are shown in 

 fig. 8. The bevelled end of the shaft of the seta is bifid. The simple tips 

 are not formed from the bifid ones by abrasion, as they are sometimes found 

 with a wing over the simple tip. In all other characters this form seems to 

 agree very closely with C. fusca. The habitat of the two forms is very 

 different, however, and further research may prove that they are quite dis- 

 tinct species. This form has since been found in Dingle Bay, in 20 fathoms, 

 associated with a fauna very similar to that found with it in Clew Bay. 



The specimens, which were found in May, were mature. 



Habitat. — Clew Bay — Dredged in 24 fms., on a bottom of sand and shells. 



Castalia fusca var. 



Another curious variety of this species was found in Ballynakill Harbour. 

 The setae resemble those of the variety hibernica, but are longer ; the tips of 

 the shafts are pointed, not bifid ; the terminal pieces are longer, with fine 

 teeth ; and the bifid nature of the tips is more obvious, and occurs in a much 

 greater proportion of the setae than in the previous variety. The character- 

 istic coarse teeth on the setae of the type form are absent in this variety also. 



This variety resembles the Kcfcrstcinia cirrata (Keferstein) of de Saint- 

 Joseph (1888, p. 324) in the following remarkable features:— In a number of 

 the segments in the middle of the body, usually the 11th to the 21st, there 

 occurs in the dorsal division of each foot a large curved aciculum, as figured 

 and described by de Saint- Joseph. These setae are present in all the speci- 

 mens which constitute the present variety. They have been notieedonly by 

 de Saint-Joseph and by Fauvel (1913, p. 57), and their significance is quite 

 unknown. The specimens were not mature, so their function can hardly be 

 sexual. The Kcfcrstcinia cirrata of various authors is a synonym of Castalia 

 fusca; but the form described by de Saint-Joseph seems to belong rather to 

 the present variety, which, if its features are constant, will require a new 

 name. 



K.I.A. PROC, VOL. XXXI. G 47 



