47 112 Proceedings of the Royal Irish Academy. 



Chaetozone viridis (Laugerhans.) 



1898. Heterociwus viridis. Caullery and Mesnil, p. 117. 

 This species, which has been described accurately by Langerhans, 

 de Saint- Joseph, and by Caullery and Mesnil, is very common in Laminaria 

 roots. It was recorded by Elwes from Torquay. 



Mature <J specimens were found in August and September. The eyes 

 are much larger than in the immature specimens, and the dorsal capillary 

 setae are longer and more numerous. 



Habitat. — Biacksod Bay — Found on the shore on 6 occasions ; dredged 



in 1 fm. Clew Bay — Dredged on 2 occasions, in 9-16 fms. 



Bofln Harbour — A mature male with large eyes and long 



swimming setae was taken in the surface tow-net at night. 



Distribution. — South coast of England; Trance; Madeira; east coast of 



United States ? 



Chaetozone alata sp. n. 



PI. XII, figs. 27 A-D. 



Three specimens of this species were obtained two from Ballynakill 

 Harbour and one from Biacksod Bay. The body is 10-12 mm. long, consisting 

 of 100-110 segments. It is very slender, and uniform in width, tapering 

 only slightly at each end. The colour of the preserved specimens is a greyish 

 brown. 



The head is conical in front (PI. XII, fig. 27a). There is a pair of dark 

 eyes deeply embedded on the dorsal side of the head, probably lying on the 

 brain. The nuchal organs could not be seen. 



The dorsal tentacles are very large, attaining a length of 2 mm. The 

 lateral cirri are 3 mm. long. The dorsal tentacles seem to be on the segment 

 in front of the first setigerous segment, each accompanied by a lateral cirrus. 

 This species is characterized chiefly by the shape and arrangement of the setae. 

 The capillary setae vary in number and length according to the age of the 

 specimen, and the following description applies to the largest individual. All 

 the specimens were immature, and probably further changes in the setae 

 occur with the advent of sexual maturity. 



Capillary setae are present in all the dorsal bundles. The longer ones are 

 slender and cylindrical with no evident flattening of the blades (fig. 27b, a). 

 The shorter ones have a distinctly flattened blade, which is very thin along 

 one edge (fig. 27b, b). In the anterior segments there are 4-6 capillary setae 

 in the dorsal bundles, but in the middle and posterior regions the number is 

 reduced to 2 or 3. Dorsal crochets appear on the twenty-first setigerous 



