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



The immber of whorls exhibits a slight difference between specimens from Gull- 

 marn and Spitzbergen on the one hand and those from Iceland and Greenland on the 

 other. In those districts there are somewhat less, in these somewhat more of the primary 

 whorls developed in specimens of equal size; thus the increase of size seems to be some- 

 what retarded in Iceland and Greenland. 



Variation of the sculpture. From Fig. 26 it is obvious that the smooth form, var. 

 Schneideri Friele 1886 or var. derugata Becher 1886, is an extreme variety, connected 

 with the coarsely sculptured forma typica through a complete series of transition forms. 

 Both the forma typica and var. Schneideri occur together in Waygat Islands and at Shoal 

 Point (see above). In the earliest whorls the first portion is always smooth, and this 

 part occupies about half the first whorl, after which the lirae begin to appear. Though 

 Becher's name is more expressive, Fiiiele's name Schneideri should be retained, as it 

 was announced in the year 1885 (by Sparre Schneider), thongh the descriptions are 

 synchronoiis. Var. tennis Jeffreys 1869: »Thinner and having fewer ridges», seems to 

 be a form between the forma typica and var. Schneideri. 



Variation of the radida. There are some slight differences in the denticulation of 

 the teeth. The median tootli in a specimen from Egedesminde (1. 14) shows a compar- 

 atively small central cusp; in a specimen from Gullmarn (1. 14.8) it is stronger, and a 

 specimen from Spitzbergen (no definite locality, Torell, 1. 13) lias a strikingly long and 

 narrow central cusp. The lateral teeth are always strongly denticulated (about 5 — 9 

 denticles in each margin); the inner uncini are usually, like the outer ones, smooth, but 

 in the specimen from Spitzbergen just mentioned they are furnished with a small cusp 

 in their outer side at a distance from the apex of about a quarter of the tooth. The spec- 

 imen forms a transition stage to the smooth var. Schneideri. I have not had an oppor- 

 tunity of examining the radula of the quite smooth variety. The radula of the Siberian 

 form is typical with a long central cusp. 



General Distribution: 



Norway: the whole coast to Vadsö, O — 40 fms (1. in Finmark: 20 mm; G. O. Särs 

 1878); Vardö in stomachs of Gadus aeglefinus (Sparre Schneider 1894); Skatören, Kjosen, 

 var. Schneideri, br. 20 mm (Sparre Schneider 1881, 1885); Tromsö, Hammerfest, 20 

 fms, var. Schneideri (Friele & Grieg 1901); Northern Norway (Verkriizen 1875; Auri- 

 villius 1886; Krause 1887; Sparre Schneider 1891); Trondhjem to Finmark, 1 — 50 fms 

 (M' Andrew 1856); Mofjord (Nordgaard 1907); Christiansund (Lilljeborg 1852*); Bergen 

 (Friele 1874); west coast, 5—106 fms (Metzger 1875); Christianiafjord, 10—100 fms 

 (Asbjörnsen 1854, Jeffreys 1870). — Väderöarna, Gullmarn, 10 — 30 fms (Malm 1855, 

 Théel 1907); Göteborg Skärgård (Malm 1858); Kullen (Lilljeborg 1852''). — Katte- 

 gatt to Öresund (Vedbsek) — The Belts to Kiel and E. of Femern (Mörch 1871; Petersen 

 1888). — Kieler Bucht (1. 14; Meyer & Möbius 1872, Lönnberg 1898, 1903). — Dogger 

 Bank (Hargreaves 1910). — All British coasts beyond the tide marks (+ var. candida, 

 Jeffreys 1867; Nichols 1900). Shetland, 78 fms (Jeffreys 1869). — N. of Hebrides, 170— 

 530 fms, var. tennis (Jeffreys 1869). — Faroe Islands (Mörch 1868). — Iceland (Mörch 



