28 THÉEL, NORTHERN AND ARCTIC INVERTEBRATES. I. SIPUNCULIDS. 
reduced to some more or less distinct folds of 
the oral disc. Hooks present or absent. Re- 
tractors mostly united to a greater or smaller 
extent: = RR EE [ES br SS On SO Ran ID ANNE 
9. Lilljeborgii KOR. and DAN. 
10. glaciale DAN. and KOR. 
11. Sarsiv KOR. and DAN. 
12. anceps mn. (?) 
13. Sabellarie n. 
14. improvisum mn. (?) 
Group I with four separate retractor-museles, two dorsal and two ventral, appears 
to be tolerably homogeneous, and with reason it may be questioned, whether the 
three last forms (margaritaceum, Hanseni and Trybomi) really represent distinct spe- 
cies. I, at least, can scarcely be said to have found any definite character distin- 
guishing them, which is expressible in words. Nevertheless, according to DANIELSSEN 
and KOREN, there are supposed to exist some dissimilarities. Thus, for instance, the 
colour of Ph. Hanseni in the living state appears to be characteristic, but yet in the 
preserved state there is no such difference to be discerned. According to the same 
authors another character of importance exists, viz. the peculiarity that the spindle- 
musecle is said to be attached to the posterior extremity of the body of Ph. Hanseni. 
Considering, however, that I never found any traces of such an arrangement in the 
three forms in question, I cannot but call in question the correctness of their state- 
ment. All the other characters, except possibly the structure of the skin, seem to 
be nothing but distinetions of degree. It may be suitable to summarize the most 
obvious distinetions in conformity with the descriptions given by KOREN and Da- 
NIELSSEN (Ph. Hanseni and margaritaceum) and myself (Ph. Trybomi). Compare, 
besides, the special descriptions below! Further imvestigations may prove whether 
these are distincetions of species or not. 
Phascolosoma Hanseni: Length of the body: 124 mm. (trunk 60 mm., proboscis 64 mm.). 
Colour in living state: trunk olive-green; proboscis lighter; throat rose-red; 
oral disk almost white, traversed by 10 red-coloured stripes; tentacles rosy. 
Colour in alcohol: whitish gray. 
Tentacles up to 180, in about 10 groups or more. 
Ventral retractors long, issuing with three roots from the anterior portion of 
the posterior third of the body. 
Spindle-muscle attached to the posterior end of the body (?). 
Skin firm, coriaceous, thick, transversely and longitudinally striate, devoid 
of true papille, but with ;iumerous minute pores of glands. 
Locality: Arctic Sea. 
Phascolosoma margaritaceum: Length of the body: 50 mm. or more (proboscis 30 mm. 
or more). 
Colour in living state: bluish white or pearl-grey. 
