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



and sometimes with a thin calcareoiis lining of the outer whorl; cuticula with 

 spiral or transversal sculpture like that in V. velutina, or smooth, forming a gela- 

 tinous coating, more or less covering the apex. Penis more or less kneed and regu- 

 larly tapering. L. 10 — 18 mm V. plicatilis (Muller 1776) 



(= Velutina flexilis [Montagu 1808], =- V. cryptospira Middendoeff 1851). 



Pl. 1, Figs. 12 — 16; TI. 5, Figs. 25, 26. 



Oncliidiopsis Bergh 1853.^ 



T. Posterior end of the foot produced far behind, its median muscular portion as well 

 as the lateral borders narrowing backwards. Penis more or less complicated by cur- 

 vation and dilatation. Primary mantle börder entirely surromiding the shell- 

 bearing part of the back. Shell oval with defined margins all around, of a carti- 

 lagineous consistency and a liglit yellowish or hyaline colour. Median tooth of the 

 radula broader than it is long (with a rectangular base); its median ciisp broadly 

 triangulär, 



A. Lateral borders of the foot-end narrower than the median muscular part. Penis 

 with a lengthened apical part, the length of which exceeds the breadth of the 

 median dilated portion. Osphradium usually of a light yellowish colour (un- 



. coloured). Inner uncini of the radula usually denticulated in their outer mar- 

 gin. Nota3um grayish with reddish brown spöts. L. max. 70 mm 



O. glaciahs (M. Särs 1851). 



Pl. 2, Figs. 17, 18, 23, 24; Pl. 5, Figs. 3, 5, 32, 33. 



B. liateral borders of the foot-end about as broad as the median muscular part. 

 Penis with a short apical part and a broadly expanded median portion. Os- 

 phradium black-coloured in its upper (basal) surface. Inner micini of the ra- 

 dula always smooth. Notseum orange-coloured. L. max. about 40 mm 



O. groenlandica Bergh 1853. 

 Pl. 2, Figs. 19, 25; Pl. 5. Figs. 1, 6. 

 II. Posterior end of the foot broadly rounded, its median muscular portion small, broad- 

 ly triangulär, the lateral borders uniformly and considerably broad. Penis forming 

 ■ a simple S-curved process. Primary mantleborder absent behind the shell, thus 

 forming a semicircular curve round the fore-part of the back. Shell semi-oval, 

 truncated and attenuated posteriorly without definite hind margin, very thin, 

 of an elastic papyraceous consistency and a hj^aline yelloAvish or a brownish colour. 

 Median tooth of the radula about as broad as it is long (witli a quadrangular base 

 plate), its cusp cylindrical, tapering; inner uncini denticulated in the outer margin. 

 Osphradium uncoloured. L. max. 35 mm O. latissima n. sp. 



Pl. 2, Figs. 20—22; Pl. 5, Figs. 2, 4, 34. 



section. 



The following survey is based oa Uie general iiivestigatious on the genus, given in the geographical 



