BISPIRA VOLUTACORNIS. 259 
and have the form of short, blunt cones. The first segment is fused with the buccal, and 
bears the first bristle-tuft. In this (anterior) region the bristles are directed upward and 
backward as conspicuous tufts, whilst the rows of hooks stretch on rounded elevations 
between them and the ventral scutes. The segments are deeply cut ventrally in this as 
in the succeeding region. The first ventral scute has two lunate depressions upon which 
the ventral lappets of the collar apparently impinge, the glandular tissue having been absorbed 
or arrested in development on these areas. The next ten scutes in the example from 
Plymouth are undivided by the median line, though three show a white streak in the 
centre—two of these belonging to the posterior region. The scutes are continued to the 
posterior end as elongated plates on each side of the median groove. 
The colour of the body is brownish violet (De St. Joseph), and there are frequently 
brownish spots on the anal segment, and in the posterior region between the bristles and the 
rows of hooks. 
The bristles of the anterior region are characterised by their golden hue and their distinct 
separation into two groups—a longer dorsal row, the long axis of which is nearly horizontal 
or slightly oblique, and a mass of shorter bristles beneath them. ‘The upper bristles (Plate 
CXXVIII, fig. 5) have very long, straight, striated shafts, tapering a little as they approach 
the tip, which is finely tapered, distinctly curved, serrated, and furnished with narrow wings, 
these indeed in some being indistinct. The bristles, moreover, show a gradation posteriorly 
where shorter forms with nearly straight tips and somewhat wider wings occur. The second 
series forms a dense brush considerably shorter than the foregoing, and, as in other species, the 
two groups are moved by separate muscles so that their special functions may be performed. 
The shafts of the longer bristles of this group are similar to those of the first series, but shorter 
and slightly stouter, and the shorter tapered tips have a trace of a curve, and wider wings, 
but soon a tendency to form a tip like a knife-blade, in which the wings are fused, is apparent, 
and by-and-by in the shorter bristles the translucent flattened tip is formed. This flattened 
blade varies in length and breadth as well as in curvature, but the majority of the bristles 
in these tufts are of this formation. The peculiar flattening of the tips, which are thinnest 
distally, gives great flexibility to the organs so that their function of smoothing and brushing 
is facilitated. All have strong, striated, golden shafts which gradually dilate from their 
translucent bases to the distal third, when gentle narrowing again occurs to the origin of 
the terminal blade. When softened and compressed in glycerine, the various stages in the 
transformation of a winged form, with an elongated tapering tip and with bold strize on the 
wings, to a form in which the tip is broad, flattened and translucent with but a trace of 
minute striation, can be followed. It resembles a pointed scalpel, only a trace of a wing 
appearing toward the convex edge (Plate CX XVIII, fig. 5a), which is serrated, the lines 
sloping outward and upward. De St. Joseph counted sixty long bristles and two hundred 
shorter in the sixth segment of an example 13 cm. long. 
With the change of feet in the second division of the body a reversion to the normal 
type of bristle takes place, the fascicles consisting of smaller, shorter bristles of nearly equal 
size with finely striated, straight shafts similar in formation to the preceding, but which 
have narrow wings—egradually disappearing on the delicately tapered tips, the minute serra- 
tions on the edges being continued far upward. These bristles are grouped in a tulip-like 
tuft. 
203 
