KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 48. N:o 1. 73 
Sculptural variation: The sculpture of S. obscura is highly varied, but no dis- 
tinet characters can be found by which the forms are separated from each other. 
Transitional stages occur between most of the forms. The typical form has usually 
an umbilical keel, but one specimen from the White Sea is destitute of it and thus is 
a transition form to var. bella. On the other hand there are specimens of the latter 
variety, furnished with umbilical cords (off Ice Fiord). Var. multilirata (Greenland) 
has a greater number of revolving ridges, more or less prominent, thus forming a 
transition stage to var. islandica with spiral grooves, but without keels. The strongest 
sculptured specimens from Greenland show relationship, on the other hand, to var. 
bella. Transition forms between the type, var. albula and var. intermedia occur at 
Murman Coast and the Kola Peninsula. As to form, however, extreme varieties differ 
a good deal from each other, e. g. var. bella, Norway, and the typical var. multi- 
lirata, Greenland. 
Variation of the radula: The number of lamellaxe amounts to 10 in var. intermedia 
and albula (from Kola-—Behring Sea), but small specimens (d. 3.2—4) of the same variety 
and from the same localities have only 6 lamell&e on each side. In specimens of var. multi- 
lirata from Davis Strait, 8 lamelle occur, but young specimens (d. 3.2) have only 6; the 
same number is found in var. bella from Grötsund. 7 lamell&e are found in the spe- 
cimens from the White Sea, which mark a transition from the type to var. bella: 
6 lamelle are found in the majority of specimens of var. bella (from Godthaab and 
72” 10' N.), in var. albula (Kildin Island) and in var. finmarchica (Finmark; young 
specimen of 3.8 mm diameter). One large specimen from Umanak was investigated; 
it had only 35 Jamelle on each side. From these statements it is obvious that the 
variation in the number of lamelle is not entirely dependent upon the growth in the 
present species, as in forms of Margarita. Moreover one qualitative character of the 
lamelle is subject to variation, namely their denticulation. Usually only the rha- 
chian and median teeth have denticulated margins, but the denticulation is sometimes 
found more or less extended to the lamelle, the first ones (Godthaab, Umanak) or 
nearly all (Davis Strait) being bilaterally serrated. Young specimens seem to have 
traces of a few denticles on both sides of every lamella (Matotschkin sharr; Vega 
Exp.) even when adult specimens of the same form have them entirely smooth. The 
rhachian tooth has a greater or less number of denticles (10—53) on each side and 
is somewhat varied in form (cfr Figs. 9—20). 
General Distribution: 
Norway: var. finmarchica, Vardö— Lofoten, 120—300 fms (d. 5; G. O. Sars 1878; 
Schneider 1891); var. bella, Vadsö— Lofoten, 30—40 fms (d. 7, G. O. Sars 1878; 
Schneider 1881, 1885, 1891; De Guerne 1886); Bogfjord (Norman 1902); var. albula, 
Vadsö—Magerö, 10-25 fms (d. 10, G. O. Sars 1878; De Guerne 1886; Schneider 
1894; Norman 1902). — Murman Coast, Nova Zembla, Arctic Ocean N. of Siberia, type 
and var. albula (Herzenstein 1893). — Barent Sea, 275—308 m, type (Knipowitsch 
1901). — Kolguev, 20 fms, var. albula (Melvill & Standen 1900). — Kara Sea, 2— 
K. Sv. Vet. Akad. Handl. Band 48. N:0 1. 10 
