194 
M UR EX. R O CK-SHELL. 
16. Murex Chordula. Twine Rock-shell. 
Shell conic, a little tapering to a rather obtuse point, 
pale chesnut-brown: spires five, rounded and well defined, 
the first occupying more than half the length, with about 
fifteen raised rounded wire-like ribs of equal diameter 
throughout, which continue over the junctions of the volu¬ 
tions, and curve in the middle towards the outer-lip; they 
are also crossed by very fine spiral stride: aperture narrow 
oval, ending in a short canal; the outer-lip thickened bra 
rib on the back ; inner-lip a little spread: length not two 
lines ; breadth the third of its length. 
This delicate species differs from M. rufus, in having 
fewer volutions, in the ribs not being protuberant in the 
middle, and in their curvature in the middle of each volu- 
tipn; it is also never half the size. 
Drifted sand, in Dublin bay. v. m . 
17- Murex linearis. Linear Rock-shell 
Montagu, pi. 9. f. 4. 
Murex elegans. Donovan, pi. 179. f. 3. 
Shell rugged, taper, glossy, light brown with generally 
a purple tip : spires seven or eight, with about ten strong 
ribs, crossed by numerous thread-like raised spiral lines, 
the summits of which are often purple: aperture oral, 
ending in a straight short, very open canal; the outer-lip 
thickened by a rib, the margin crenate by the incurvation* 
of the spiral lines, and toothed within j pillar-lip smooth: 
length a quarter of an inch or more: breadth about aline. 
Western coasts, and Dublin bay. v . v, 
18. Murex purpureus. Purple Rock-shell 
Montagu, pi. 9. f. 3. 
Shell very rugged, tapering to a very fine point, dark 
purple with often white blotches : spires nine or ten, 
rounded, with about twenty ribs running a little obliquely 
to the right, and crossed by numerous sharp raised trails- \ 
verse ridges, which rise into angles on the ribs, and give 
the shell a very rough or cancelled appearance: aperture I 
pval, ending in a short straight canal; the outer-lip thin 
with a white margin, crenate by the outward striae; inside I 
