152 SYSTEMATIC ARRANGEMENT 



arched, curved, denticulated on each side; outer central strong; 

 lateral teeth numerous, hair-like, innermost rather larger. 



The mantle of Gibbula magus shows an incomplete, tubular, bran- 

 chial fold ; head-lappets two, suboval, approximating, large, long, 

 fimbriated on the edges, hanging over the head ; lateral vibracula 

 3 • 3, fimbriated ; neck-lappets large, suboval, the columellar one 

 two- or three-lobed, the dextral one plain ; operculum of five or seven 

 spiral turns. — Clark, Moll. 311. 



The two head-lappets of Gibbula cineraria almost coalesce, form- 

 ing a crenated veil ; the neck-lappets are suboval and well-developed, 

 that on the pillar side with three or four thick, subcylindrical, pendent 

 fillets from the lower edge, the other plain ; lateral vibracula 3 • 3, 

 sheathed at the base ; operculum serrated on the edge. — Clark, 312. 



Teeth of Gibbula cineraria numerous, in curved cross lines ; cen- 

 tral elongate ; inner lateral 5 ■ 5, rather oblique, with a transverse 

 hook at the apex, gradually larger externally ; outer one with large 

 hooks ; outer lateral numerous, hair-like, hooked. 



Central tooth of Gibbula cineraria heart-shaped, produced at the 

 base in the middle, above contracted by a short neck on both sides, 

 rounded and winged, forming a transverse oval head ; cutting edge 

 transverse, denticulated ; lateral teeth on each side five, imbricated, 

 shaped like the half of the central one, but towards the sides gradually 

 changing in shape ; the neck wider, cutting edge oblique, and fur- 

 nished with a plate directed inwards, in the last the plate is large 

 and subquadrate. Lateral series of teeth on each side about ninety, 

 slender, with a plain hook, linear, gradually diminishing, in the last 



Fig. 82 — Teeth of Gibbula cineraria. 



obsolete, in the inner ones denticulated only at the base, in the 

 middle ones on all sides ; scape compressed, in the first furnished 

 behind with a wing, in the middle ones simple, produced under the 

 hook, slightly bent towards the base, attenuated, in the last lamina- 

 ceous (fig. 82). 



The head-lappets of Gibbula umbilicata are small, very anterior, 

 distinctly separated, and fringed with six short cilia ; the neck-lappets 

 are large, the pillar one fringed, the other plain, sinuated; lateral 

 vibracula 3 ■ 3, sheathed ; operculum multispiral. 



The two head-lappets of Gibbula tumida are small, delicately 

 denticulated ; the neck-lappets are large and discordant, the pillar 

 one gently scalloped ; the right one is largest, plain-edged ; tentacula 



