2 ARKIV FÖR ZOOLOGI. BAND 8. N:0 25. 



specimen cut into sections. From this examination it was 

 evident that the new mollusc is an opisthobranchiate gastropod 

 most closely allied to the northern and arctic genus Diaphana. 



Localities. The recent specimens of Ptisanula lim- 

 nceoides belonging to the Riksmuseum, were dredged by To- 

 rell in 1858, partly in Bel Sound at 5 — 12 fms, stones, algae 

 (6 sps), at 30—40 fms, stones with Hydrozoids 1 (1 sp., sec- 

 tioned), and at 30 fms, fine clay (1 sp.), and partly in Horn 

 Sound, at 40 — 60 fms, clay, stones (1 sp.). The fossil shells 

 from Kapellbacken were found in four different horizons of 

 a layer, belonging to »the finiglacial transgression». At 22, 

 24, 25 and 26 m above the sea there were collected 1, 3, 3 

 and 1 specimens respectively. 



Description of the Shell. 2 It is of an elongate ovate 

 shape with an elevated blunt-tipped spire and high, slightly 

 convex whorls, tabulated at the oblique, channel-shaped su- 

 tures. The colour is semi-hyaline white with a shining sur- 

 face, covered, in a fresh state. by a thin, straw-coloured, 

 feebly gleaming cuticula with some longitudinal stripes of 

 darker brown. The aperture contains half the length of the 

 shell and has an oblong or rounded rectangular form with 

 an obtuse upper angle; the outer margin issues at right 

 angles from the body-whorl, bends immediately down, is in its 

 middle-part somewhat concave or else feebly convex, strongly 

 and uniformly bowed below, and then directly passing into 

 the columellar margin; the pillar is in its lower part sinuous 

 and furnished in the middle with a distinct convexity that 

 is not sharply marked as a fold ; in its upper part again it 

 is slightly concave or nearly straight. The columellar and 

 outer margins are connected on the parietal wall by a fine 

 calcareous lamella. The columellar margin is reflected in its 

 whole length, thus forming a narrow but deeply protruding 

 umbilicus. The apex is twisted regularly with a somewhat 

 depressed nuclear whorl. The surface is smooth with the 

 exception of fine irregularly placed lines of increase. Besides 

 them very feeble traces of a few distant opaque spiral lines 



1 Chiefly Campanularia integra Mc Gill and Sertularella tricuspidata 

 Ålder. 



2 The Description of the shell and its variation has been published 

 in Geologiska Föreningens i Stockholm Förhandlingar Bd 35, H. 5, Maj 1913. 



