306 TROCHID®. 
with a red-brown narrow longitudinal medial line; when 
fully on the march, it loses the auricular angles, becoming 
posteally narrowed and elongated into a sharp point: the edge 
of the main sole is clothed with a short, close, exceedingly fine 
white fringe, only visible in water by the aid of a good lens; 
it is an error to describe it as crenated ; the colour beneath is 
yellowish-white, above lemon-yellow, sprmkled with irregular 
fine brown lines and pots. When not in extension it has a 
papillose aspect, but in full action appears divided by fine 
anastomosing lines into irregular lozenges, resembling coarse 
shagreen : from the upper surface a membrane or lobe springs, 
carrying its walls erect, on which, at some distance from its 
posterior origin, is imbedded a circular multispiral corneous 
operculum, having the close-set striz of mcrement crossed by 
fine oblique les; the accessorial lobe then pursues its course 
on each side the main foot to nearly the anterior end, the 
margins being clothed with strong, rather coarse white fringe ; 
and in addition, on each side, there are four longish, cylin- 
drically tapering, pomted, equidistant white vibracula, that 
issue from a tubercular sheath, into which they can be par- 
tially retracted; these appendages are in constant motion. 
The internal organs present no unusual peculiarity, except the 
reproductive elements and branchial plume, which, as they 
offer some anomalous pots, will be mentioned at the end of 
the specific descriptions. 
This beautiful creature is an inhabitant of the coralline 
zone, at Exmouth, very rarely appearing in the littoral or 
laminarian limits ; the pure snow-white variety is occasionally 
taken at the same place. Our remarks are perhaps too 
diffuse, but this species is selected as the type of this section, | 
though, from the similarity of the tribe, almost any other 
would have served. 
T. zizipHinus, Linn. et Auct. 
T. ziziphinus, Brit. Moll. ii. p. 491, pl. 67. f. 1-6. 
The animal inhabits a strong, conical, brown or white shell 
of 6-8 spiral, smoothly striated volutions. It is nearly similar 
to the T. granulatus ; the principal variations are in the foot 
