SPIRORBIS VIOLACKUS. 389 
The ordinary S. violaceus has been found elsewhere in Greenland (Levinsen); British 
Columbia, on shells (Bush) ; Spitzbergen (Fauvel) ; Vancouver Island (Pixell). 
The cephalic collar is normal and forms a sheath for the branchiz which are about four 
in number on each side, and do not offer any noteworthy peculiarity. 
The operculum is circular and hollowed out distally like a saucer, with a short stalk, or 
process like a reversed cone. In young examples it is circular, forming a saucer-shaped 
disc, but in the older forms it is sometimes nail-shaped ; that is, the circular shape is lost 
by an extension of one edge toward the stalk. Externally is the clear outer investment of 
the rim of the operculum, within which is a radially arranged layer at right angles to it ; 
then follows a broad belt of circular fibres with strong longitudinal fibres converging to 
the stalk. The calcareous investment is very brittle. 
The body is typical in outline, and has three bristled segments. The first or collar series 
(Plate CX XXII, figs. 3a, 3b, and 3c) consists of bristles which have no distinct gap at the 
base of the tapered terminal blade, or a modified one. The former kind occurs in one group, 
the straight shaft slightly dilates at the shoulder, from which the tip is bent backward and 
coarsely serrated, the serrations next the shoulder being perhaps less distinct than those 
which follow. The other group presents a distinct differentiation of the base of the terminal 
blade, the separated part at the shoulder having finer serrations, the edge beyond (bearing 
the marked serrations) being separated by a distinct step. The base of the blade has five 
or six teeth, at least, in lateral view, and antero-posteriorly this part appears to form a spiked 
collar to the anterior edge of the bristle. The serrations on the terminal blade vary, that 
figured being one with coarser points. There is much in the structure of the collar-bristles that 
agrees with S. vitreus, O. Fabr., for in that form a series of stages occurs—from the bristle 
without a trace of a gap—to one in which there 1s a modified gap, which forms a wide indenta- 
tion at the base of the tip, and which includes the serrations of the basal double web as shown 
by Mesnil. The second bristle-tufts of the region have straight shafts and tapered, winged 
tips, bent at a slight angle (Plate CX XXII, fig. 3). The bristles of the third tuft have in 
the group a slightly curved tip (sickle-shaped), with the serrations only at the tip, as described 
by Caullery and Mesnil. 
The bristles of the posterior region have broad, tapering tips, bent nearly at a right 
angle, with the edge coarsely serrated. 
The hooks (Plate CX X XVI, fig. 20) are very thin and diaphanous, and it is not easy 
to get a perfect lateral view. The anterior edge is straight, very finely serrated, and ends 
inferiorly in a larger spike or main fang. The upper edge is convex next the serrated border, 
and slopes slightly downward to the thin posterior edge. The lower margin leaves the main 
fang with scarcely an incurvation. These thin hooks readily assume various outlines, 
especially anteriorly. | 
The tube (Plate CX XXII, figs. 3d and 3e) is vitreous and peculiarly coiled so that the 
aperture is on the summit of the spire. The whorls are boldly ridged, and the ridges affect 
the shape of the aperture, which is sometimes transversely elongated. The whorls thus 
form a conical mass with a flattened under-surface, in the centre of which is the primary coil. 
The shape is therefore like an irregular blunt cone, and the shell is very hard and glistens like 
pinkish porcelain. In lateral view the tube quite differs from S. violaceus of O. Fabricius 
and Levinsen, the latter showing a flat spire of a different character, the aperture, for instance, 
