KUNGL. SV. VET. AKADEMIENS HANDLING Ali. BAND 41. N:0 4. 



2. Shell without umbilicus and stria?; columella not folded; apical perforation 

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



II. Spire prominent. 



A. Outer lip not extended onto 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; 

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

 = 2 A 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). 1 



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

 opaque, white or creamy, its breadth = V 6 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 4. shell ovate (its breadth = r, /» °f the length), white with a yellowish 

 cuticula. L. 7 — 8 mm. 1!. Gouldi (Couthouy 1839). 



2. Apex slender and wart-like, shell cylindrical (its breadth 1 U of the 

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



Vol villa A. Adams 1850. 



Shell convoluted, sculptured with very fine spiral stria? 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 (Brtjguiere 1792). 



Fam. Scaphandridse. 



I. Stomach with 3 calcareous plates ; foot truncated 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 by 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, triangular; colu- 

 mella forming a central pillar, slightly sinuous Atys Montfort. 



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

 slightly widened below; spiral stria? not punctured, often absent; cephalic disc 

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

 forated Cylichna Loven. 



' Leche describes (1878) another var. elongata with the spire elevated. 

 Whether I!, obtusa is a distinct species or only a southern form of I!, pertenuis is a doubtful point, 



