176 Prof. M‘Intosh’s Notes from the 
strize cross the body of the hook obliquely. The number 
of hooks in these long rows is great, and the pigment-line 
indicating them remains after removal of the cuticle and 
hooks. 
The posterior hooks have the posterior outline con- 
siderably lengthened, so as to alter the character of the 
hook and give it a resemblance to that often seen in the 
Ampharetide and Terebellide. They have four teeth above 
the chief fang, which is proportionally larger than in front, 
and the basal outline is slightly convex. Oblique striz are 
also present on the body of the hook. The ligament, as in 
the anterior hooks, is attached to the angle between the 
posterior outline and the base. 
Dorsally the edge of the alar membrane in the fourth 
form, Serpula vermicularis, L., is continuous with the collar 
on each side—a considerable gap, however, intervening 
between the points of attachment. ‘The collar then passes 
on each side as a deep frilled lamella to the mid-ventral 
line, where it is continuous with that of the opposite 
side. The mouth opens between the branchie nearer the 
ventral than the dorsal border ; dorsally it has the ciliated 
upper lip, and ventrally the ciliated lower lip, whilst below 
the latter is a triangular area. 
The branchiz, which are from 30-32 on each side, form 
two fans of moderate length, and are tinted of a fine red 
hue near the tip. Each filament diminishes toward the 
extremity and ends in a long tapering process. The cuticle 
is thick, and the longitudinal and circular muscles well 
developed, but no chordoid skeleton is present. The pinne 
are of moderate length, the longest being about a third of the 
length from the tip, and they taper from base to apex, and 
likewise show no chordoid skeleton. Their colour is variable, 
reddish with white bars, entirely red or white, with darker 
zones ; sometimes the base is red and the rest white. The 
pinne take their hue from the bars of colour of the region 
to which they are fixed. In very young examples the base 
is red, and the filaments greenish from the blood. 
The opercula spring from the dorsal edge of the branchial 
fans, that on the one side being short and rudimentary, 
whilst that on the other forms a finely fluted vase supported 
on a stalk, which gradually expands as it passes upward to 
the fluted cup, which has from fifty to a hundred or 
more denticulations (a hundred and six, De St. Joseph). 
In many cases the functional operculum is on the 
left, in others on the right. The distal cup is hollowed 
