KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 50. N:0 5. 7 



with a callous dilatation above the umbilicus on the body-whorl; the inner 

 uncini with 2 cusps of uniform or unequal strength Lunatia Gray 1847. 

 2. Shell smooth, elevated, globose wdth a fibrous, silky cuticula, a canalicu- 

 lated suture and a narrow fissure-like umbilicus; columellar margin without 

 callous dilatation on the body-whorl; the inner uncini with 2 cusps of uni- 

 form strength Amauropsis Mörch 1857. 

 B. The median tooth of the radula with 1 cusp only; the laterals simple; the inner 

 uncini with 2 or 3 uniform cusps. Shell globose, thin; whorls convex, of ten 

 flattened below the simple suture; columellar margin forming a deep sinus with 

 the body wall; umbilicus covered by a thin callus Acrybia H. & A. Adams 1853 



(= Ampulhna Lamarck of G. O. Särs 1878). 



Natica AdaNson 1757. 



I. Umbilicus wholly covered by the callus; whorls of ten somewhat concave below the 

 suture, smooth, or \nth ill-defined strise; colour wliitish to brownish. Operculum 

 unicoloured, opaque grayish or yellowish, nucleus of the same colour, rarely darker. 

 H. of the shell 10 — 40 mm N. clausa Broderip & Sowerby 1829. 



Pl. 3 Figs. 1—3, 5—14, 16, 17; TI. 5 Figs. 7—14. 



II. Umbilicus only half-covered by the narrow callus and forming a narrow but open 

 slit, protruding under the callus; whorls tumid, with feeble, ill-defined spiral striation; 

 colour whitish. Operculum transparent yellowish white with a well-marked dark 

 brown nucleus. H. of the shell about 10 mm N. bathybii Friele 1879. 



Spire considerably elevated. H. about 15 mm var. oblonga Friele 1886. 



Pl. 3 Figs. 4, 18; Pl. 5 Fig. 15. 



Lunatia Gray 1847'. 



I. Inner uncini of the radula having cusps of very unequal size, the outer one always 

 much smaller, shell dotted, banded or unicoloured. 



A. Shell with brown döts set in regular rows; umbilicus open, rounded, only its 



upper part covered by a callous dilatation of the columellar margin. Median 



tooth of the radula broad (its length usually < V2 its breadth)-. 



1. Whorls somewhat compressed at the shallow suture, coloured all över 



with brown döts in spiral arrangement; upper angle of the aperture filled 



with a strong projecting callus, separated from the outer lip by a narrow 



groove; umbilicus surrounded by a blunt ridge and with a few obscure ridges 



' Natica (liunatia) sphsroicles, briefly described by Jeffreys in 1877, has been excluded from the follow- 

 ing scheme (as well as from the geographical section of tliis publication) because of the insufficient descrip- 

 tion given, it being based on a very young shell. — »Natica sordida Sws.», mentioned by Murch 1871 and 

 Petersen 1888, is also omitted as a very douhtful member of the Danish fauna. 



^ For the radula of L. catena see Troschel 1856 — 63 (the specimen examined was found in the Categat). 



