22 SYSTEMATIC ARRANGEMENT 



** Operculum suhcircular ; nucleus subcentral, within the margin. 



2. B. Humphreysianum. 



3. B. glaciale. 



The central tooth of Buccinum undatum pectinated, with 7 denticles ; 

 the scape of the lateral tooth three-toothed, the basal denticles the 

 largest (see fig. 1. p. 3). — Lov6n, t. 5. f. 4. 



The central tooth of Buccinum cyaneum with 5 denticles ; the 

 lateral teeth acutely angulated, the scape two-toothed, the basal 

 tooth much the broadest. — Love'n, t. 5. f. 5. 



Dr. Loven figures Buccinum, undatum as having seven toothlets on 

 the central, and three on the base of each of the lateral teeth (t. 5. 

 f. 4) ; Chrysodomus antiquus (t. 5. f. 1) as having three denticulations 

 on the central, and three lobes on the basal part of the right, and 

 two on the basal part of the left lateral tooth. The teeth of these two 

 genera have been exhibited and sold in London as the teeth of the 

 two sexes of Buccinum undatum, the animals of which are both sold 

 under the name of Whelks. 



12. Gastridia. 

 Shell top-shaped, solid ; spire short ; mouth ovate ; outer lip with 

 a strong tooth in front ; inner lip very thick, callous ; canal short. 

 Operculum oblong, rounded at each end ; nucleus small, in the centre 

 of the outer edge ; scar very large, shaped like and nearly as large 

 as the operculum, with a thicker margin on inner sides and ends. 

 Animal and teeth unknown. 



1. G. plumbea, Adams, Gen. Moll. t. 13. f. 8, shell and operculum. 



Fam. IV. PUSIONELLAD^. 



Head small. Mantle enclosed. Teeth ? 



Operculum horny, half-ovate ; nucleus on the 

 middle of the straight inner side (see fig. 11). 



Shell fusiform or turrited ; canal rather produced, 

 bent up at the end ; pillar simple, smooth. 



1. Ptjsionella. 



Shell fusiform or turrited, smooth, covered with a thin, hard, 

 polished periostraca; whorls smooth ; mouth ovate; outer lip simple 

 acute, inner smooth ; pillar with a short, acute fold at the base of 



the short open siphon. Animal ? Teeth ? Operculum 



horny, half-ovate ; nucleus on the middle of the straight inner side. 



1 . P. Nifat. 



2. P. buccinata, Adams, t. 24. f. 3, operculum. 



3. P. aculeiformis. 



