KUNGL, SV. VET. AKADEMIENS HANDLINGAR. BAND 41. N:0 4. 11 



2. Shell without umbilicus and striae: coliimella not folded: apical perforation 

 narrow; colour white. L. 3 mm. R. nitidula (Loven 1846). 



II. Spire prominent. 



A. Outer lip not extended unto the apex, which is flattened and spirally twisted; 

 whorls 4; no spiral sculpture: umbilicus minute or none. 



1. Whorls sligthly angulated at the suture; columella mostly without fold; 

 sliell transparent, whitish or light brown ; spire low ; breadth of the shell 

 = V3 of the length. L. 2,5 mm. R. pertenuis (Mighels 1839) 



= semen (Reeve 1855). 

 Spire elevated ; whorls step-like. L. 3,5 mm. 



var. turrita (Möller 1842).' 



2. Whorls rounded at the suture; columella with an obscare fold; shell 

 opaque, white or creamy, its breadth = V-, of the length. L. to 7 mm. 



R. obtusa (MoNTAGU 1803).' 



B. Outer lip as high as the apex; shell spirally striated. 



1. Apex flattened; whorls 1. sliell ovate (its breadtli = ■''/** of the length). white with a yellowish 

 cuticula. L. 7 — 8 mm. E. Gouldi (C^ouTHOur 1839). 



2. Apex slender and wart-like, shell cylinclrical (its breadth = ^1-. of the 

 length), white and subpellucid. L. 3 mm. R. mamillata (Philippi 1836). 



Volvula A. Adams 1850. 



Shell convoluted, sculptured with very fine spiral strise towards the ends ; 

 colour white, transparent; columella a little thickened; aperture very narrow, wider 

 at the lower end. L. about 3,5 mm. V. acuminata (Bruguiére 1792). 



Fam. Scaphandridae. 



Stomach with 3 calcareous plates ; f oot truneated or slightly bilobed behind ; 

 parapodia present; shell opaque, with the spire concealed. 



A. Radula 1.1.1; aperture of the shell much dilated below; spiral striae punc- 

 tured; animal with the cephalic disc produced behind in two lobes. 



1. Vertex of the shell covered b}^ a callus, imperforate; laterals of the radula 

 long, arcuated; columella concave; animal not perfectly retractible into the 

 shell Scaphander Montfort. 



2. Vertex of the shell perforated; laterals of the radula broad, triangulär; colu- 

 mella forming a central pillar, slightly siniious Atys Montfort. 



B. Radula (2 — 5) . 1 . 1 . 1 . (2 — 5), laterals claw-like; aperture of the shell usually 

 slightly widened below; spiral strise not punctured, of ten absent; cephalic disc 

 truneated, without lobes; animal retractile into the shell; vertex not per- 

 forated Cylichna Loven. 



' Leohe descnbe,s (1878) another var. cluiujata with the spire elevated. 



- Whether K. obtusa is a distiiict species or only a southerii form of R. pertenuis is a doubtful point. 



