90 THÉEL, NORTHERN AND ARCTIC INVERTEBRATES. I. SIPUNCULIDS. 
Phascolion tuberculosum THÉEL 1875". 
Pl. VI. Figs. 96—098, Pl. VII. Figs. 99—108, Pl. XV. Fig. 209. 
Phascolosoma pallidum KOREN and DANIELSSEN 1875 and 1877. 
Phascolosoma strombi v. verrucosum KOREN and DANIELSSEN 1877. 
Phascolion pallidum SELENKA 1883. 
Phascolion strombi Vv. verrucosum SELENKA 1883. 
Phascolion strombi v. tuberculosum NORMAN 1894”. 
Habitat: 
West Coast of Sweden: Koster, sand, 15—20 fms. (LJUNGMAN ””/s 1865), about 
100 specimens, probably not living in shells of Molluses nor in tubes of worms. — 
West Coast of Norway: Bergen Fjord, mud with sand, 200 fms. (KOREN and Da- 
NIELSSEN), 1 sp. living in the tube of Pectinaria auricoma (Mus. B.). — Trondhjem 
Fjord, Rödberg, mud, 100 m., 1 sp. and Hjeltefjord, mud, 100 m., 2 sps. (Mus. L.). 
Distribution in General: 
Further investigations of the ocean may prove that the species in question has 
a much wider distribution than is now believed and possibly that the West Coast of 
Sweden is its present centre of distribution. However, it is very likely that it may 
be dredged up in great numbers in several other localities. ; 
In 1877 KOREN and DANIELSSEN wrongly referred Phascolion tuberculosum to 
the variety ""verrucosum'" of Phascolion strombi, and later on their example is followed 
by SELENKA, who evidently based his opinion solely on the statements of those earlier 
investigators. In the same year the Norwegian investigators described in detail and 
figured the species Phascolosoma pallidum, established by them in 1873. As far as 
I have been able to ascertain, this form bears the closest relation to Pascolion tuber- 
culosum and can scarcely be kept separate from it. According to the information 
given by KOREN and DANIELSSEN, it is true, there exist some differences between 
them, apparently, but for my own part I am fully convinced that these supposed 
differences are due to an abnormity in the structure of the single specimen examined, 
or may be even to insufficient observation. Thus, the fact, that the longer dorsal 
retractor was split anteriorly, so as to transmit a loop of the intestinal canal, may 
depend upon an individual abnormity. Besides, it is a misleading statement of KOREN 
and DANIELSSEN, when they speak of a "longer" and a "shorter" retractor, instead 
of a dorsal and a ventral one (or, according to my view, one dorsal and two ventral 
ones). Their own figure plainly exhibits this, the ventral retractor being bifurcate at 
its posterior point of attachment. Seeing this is the fact, it cannot but seem incom- 
prehensible when they write: "the nervous cord runs as usual between both retractors.'' 
1 Comp. the introduction of this report! 
> Ann, Magaz. Nat, Hist, XIII. Ser. 6. London 1894. 
