ETEONE ARCTICA. 103 



there are certain differences, such as the shape and length of the ventral cirrus, which 

 Malmgren states is sub-obtuse and distinctly longer than the setigerous lobe. It differs 

 from E. longa l in the shape of the dorsal cirrus and other points. The condition of the 

 proboscis prevented the determination of the number of the terminal papillas. 



A form which has been described as a separate species, though apparently only a 

 variety of Meone arctica, merits a special description from its characteristic structure. 



Eteone arctica var. Robertiana. Plate LXIX, figs. 8 and 9 — feet. 



Head flattened, bluntly conical, with a distinct furrow on each side. Two subulate 

 tentacles. ~No visible eyes in the preparation. The fused cephalic and peristomial 

 region is separated by a constriction from the succeeding segment. The tentacular cirri 

 are little tapered and considerably shorter than the transverse diameter of the region. 

 Body of the typical form, terminating in two linear fusiform or almost cylindrical cirri. 

 Pale, slightly iridescent. Dorsal cirrus ovoid at the tenth foot and shorter than the 

 setigerous process, ovato-lanceolate at the thirtieth and projects further outward than 

 the setigerous process. Still further backward it becomes more acutely lanceolate and 

 the peduncle is longer. Setigerous lobe largest anteriorly, bifid, and carries bristles, the 

 shafts of which have dilated tips with a larger and a smaller curved hook and minute 

 spines passing downward to the shoulder. The terminal blade is of average length, is 

 broad at the base, tapers gradually to a fine point and has a serrated edge. The ventral 

 cirrus is lanceolate, about as long as the setigerous process at the tenth foot, and some- 

 what longer and more acuminate posteriorly. 



Synonyms. 



1874. Eteonella Robertianse, Mcintosh. Ann. Nat. Hist., ser. 4, vol. xiv, p. 197. 



1875. „ „ Idem. Invert, and Fishes St. Andrews, p. 120. 



Habitat. — Found when digging for littoral Annelids near low-water mark at the 

 West Rocks, St. Andrews (R. M.). Other pale specimens were sent alive (E. M.). 



Head differs from that of the ordinary form by the more evident separation of the 

 fused cephalic and peristomial segments — a constriction dividing them from the succeeding 

 region. The head has a flattened bluntly-conical form with a distinct furrow on each 

 side, and with two short subulate tentacles on each side anteriorly. Two minute but 

 distinct papillse occur dorsally in the centre of the peristomial segment immediately behind 

 the head. Posteriorly the peristomial segment seems to form a boss at each side, from 

 the posterior part of which two slender and little tapered tentacular cirri proceed. In 

 the preparation they are considerably shorter than the transverse diameter of the region. 



1 Some examples of E. longa from Greenland have many small white ova, showing a distinct 

 micropyle, attached to the bristles and other parts. 



