66 N. ODHNER, NORTHERN AND ARCTIC INVERTEBRATES. VI. PROSOBRANCHIA. 2 SEMIPROBOSCIDIFERA. 



Median value of Formål Variation, 18 sps measured: 



length of sliell 

 breadth » » 

 lieiglit » » 

 lengtli 

 breadth» 

 whorls . 



aperturo 



7—8 

 5.3-G.4 



2.9—3.0 

 0.2—7.0 

 40— C). 1 

 about 2 



9—10 

 6.7—7.9 

 3.0—4.2 



7 7— O -. 

 0.3-7.8 



2 



12—13 

 9.1—10.4 



4.7—5.7 



10..';— 12 

 9.1-10.2 



2 + 



ax. 18 (Horn 



Sonnd) 



14.5 





9 





16 





14.3 





9 1/ 

 - 12 



1 



A comparison of these numbers with those of V. velutina from Spitzbergen will 

 show that V. lanigera falls within tlie limits of tlie variation of that species, but tliat 

 tlie whorls are somowhat less developed. In V. vehitina of the same size there is about 

 one half whorl more than in V. lanigera. This is diie to the fact that the earliest 

 whorls of the present species are more inflated and broader. 



The scnlpture of the shell presents the interesting fact, that the earliest whorl 

 is furnished with continiions spiral cuticular keels; after the first whorl these become 

 discontinuous, dissolved in crests and further on produced in hairs. A smooth propor- 

 tion of the embryonal conch, such as occiirs in V. velutina, does not exist; it is furnished 

 with ridges right from the beginning. Just in this particular we find the explanation of 

 the smaller number of whorls. V. lanigera in its development omits the smooth stage 

 passed through by V. velutina, and it enters directly into a V. velutina stage, that con- 

 tinues during the formation of the first whorl. V. lanigera consequently represents, in 

 relation to V. velutina, a directly advanced stage with reduced development. It has 

 a thicker cuticula but a very thin calcareous layer of the shell; in the last respect there 

 is a great resemblance to V. Schneideri; owing to the thicker cuticula or coriaceous outer 

 layer, it approaches V. plicatilis. The aperture varies in extension; the outer lip may 

 project considerably beyond the aperture, which causes a sunken apex, or it is less ex- 

 panded, by which the spire becomes somewhat more prominent. 



The radula has strongly denticulated median and lateral teeth. The median tooth 

 has a short and broad central cusp and strongly sinuous margins of the basal plate, The 

 laterals have also a sliort and broad cusp and about 6 denticles on the sides of it. Two 

 radula^ (from Spitzbergen, no definite locality, and Norwegian Islands) were examined 

 and seem to agree entirely in their construction. 



Goiioral Distribiif ioii: 



Norway: Lofoten to E. Finmark, 30—40 fms (1. 13, G. O. Särs 1878); E. Finmark 

 (Norman 1902); Tromsö, 10—20 fms (Sparro Schneider 1885; Friele & Grieg 1901). — 

 North Atlantic, St. 280 and 323, 35 and 223 fms (Friele & Grieg 1901). — W. of Beeren 

 Island, 74° 15' N. 16° 50' E., 250 m (Friele 1902). — Spitzbergen, off South Cape, St. 

 336 and 338, 70—146 fms (Friele 1879; Friele & Grieg 1901); E. Spitzbergen (Krause 

 1892). — Franz-Josepl) Land, 10—30 fms (Melvill & Stånden 1900). — W. Greenland 

 (Posselt & Jensen 1899). Depths 4 — 223 fms. Clay, sand, stones, rocks. 



