Clare Island Survey — Archiannelida and Polychaeta. 47 73 



fathoms, and these specimens are partly utilized in drawing up the following 

 description. The colour is greenish-yellow in the preserved specimens, and 

 is especially concentrated in the cirri. The largest specimen has 38 segments 

 and is o£ mm. long. The smallest is 2 mm. long and also has 38 segments. 

 The head is rounded in front, broader behind, and bears four long slender 

 tentacles (PL VIII, figs. 19 A, b). No trace of eyes could be seen in any of 

 the specimens. The mouth is a wide transverse opening on the middle of 

 the ventral side of the head. Between the head and first segment on each 

 side there is a deep ciliated groove, containing the nuchal organs. The first 

 segment bears a single pair of tentacular cirri. On the second segment there 

 are two pairs of cirri, the dorsal pair being somewhat the larger. All the 

 tentacular cirri are seated on short pedicels, have swollen bases, and long 

 filiform tips. The second segment has a well-developed setigerous lobe on 

 each side. The third segment is normal, but has no dorsal cirri. The dorsal and 

 ventral cirri of the following segments are round or broadly oval. The anal 

 segment bears two large oval cirri, between which is a short papilla (fig. 19 c). 

 The shaft of the setae (fig. 19 d) terminates in a slightly swollen bevelled 

 head and two long equal claws, of which only one is seen in side view. 

 These claws are covered with spines, and between them rises the terminal 

 blade. The latter is long and slender, minutely serrate, and with oblique 

 striations. 



This description agrees closely with that of Theel, whose specimen was 

 10£ mm. long, with 48 segments. It differs only in the absence of the two 

 large black eyes which Theel found. In the same year that Theel described 

 this species, Langerhans published a description of a Polychaete from 

 Madeira which he called Mystides caeca. It differed from the northern form 

 in having no eyes, thus agreeing with the Irish specimens, but this can 

 hardly be considered a valid specific character, as the eyes often disappear 

 in preserved specimens. In other respects the two forms are so much 

 alike that I have no hesitation in regarding them as the same species. 



The Mystides viridis of Webster & Benedict (1887, p. 712) appears to be 

 this species. The authors state that they had not seen Th^el's paper. 

 The shape of the head, tentacles, tentacular cirri, feet, setae, and anal 

 cirri all agree with Theel's species. Eyes were present on the head. The 

 authors do not state whether setae are present on the second segment, 

 and the figures give no information on this point. 



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



shells. 

 Distribution. — Nova Zembla ; Madeira ; Monaco ; Eastport, Maine. 



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



