either dorsally or ventrally, though it may represent in the dorsal region part of the
segment in front.
The following segment carrying the second pair of gills has a broad fan-shaped flap
at each side about midway between the gill and the ventral scute, whilst the following or
fourth segment bears the third branchia and the first setigerous process. The ventral
scutes in the example are not separated by the deep furrows so characteristic in other
forms, but appear to be nearly continuous from the anterior broad scute to the narrow
median ridge about the eleventh bristle-tuft. All the segments are marked by narrow
rings. The general colour is yellowish, the ventral scutes rufous brown shaded with
purplish black (Montagu). Gravier describes the forms from the Red Sea as greenish
grey, with bold bars of brown on each thoracic segment, and white at the insertion of the
dorsal bristles. The ventral tori are underlined by dark bands with a touch of the same
colour at the cushions. The latter are reddish. The abdominal tori are white, set like
pearls in a base of grey pigment. The tentacles have brown rings. The branchias are
comparatively small, distinctly separated, and with short stems, the usual gradation
occurring from the first to the third. They are distinguished from all the others by their
very finely branched terminal divisions. The main stem and its subdivisions are
short so that the entire organ in each case projects proportionally little. It is
dichotomously divided. The branchias of the Mediterranean L. medusae, though also
furnished with fine terminal ramuscules, are more lax in branching, the separate divisions
being longer.
Seventeen pairs of prominent setigerous processes occur ^anteriorly, and the bristles
are directed outward and backward. Bach consists of a flattened brush, with the edges
dorsal and ventral, of pale golden bristles, the tips of which are in two series, a longer
and a shorter. Each bristle (Plate OXXVI, fig. 1) slightly dilates above its' pale bulb to
near the origin of the wings, then tapers to a fine point. The wings are of moderate
breadth, and cease before reaching the delicately tapered tip. The bristles of the shorter
series have the same structure, but their shafts are more slender. They extend about as
far as the commencement of the wings of the longer series. No noteworthy difference
between the .first and the last tuft occurs.
The rows of hooks commence at the second bristle-tuft, and are long in front,
diminishing in length backward to the ninth or tenth, and again increasing at the
fourteenth setigerous process, that is, behind the median frill which succeeds the scutes,
only a brief, space separating the long rows in the mid-Ventral line, and the same
condition is found at the fifteenth. At the sixteenth and seventeenth setigerous process
the rows are shorter, as also is the mid-ventral space between them. The uncinigerous
lamellae which succeed are almost ventral in position, being separated only by the
narrow ventral surface (Montagu’s dorsum), and they continue to the posterior end
(absent in the example). Double rows of hooks occur from the seventh to the sixteenth
{fide autor.).
The hooks (Plate CXXVI, fig. 1 a) have a long anterior border with four or five
teeth in diminishing series above the chief fang, making five or six in all, and there is no
process on the edge of the base beneath the main fang. The posterior outline is boldly
convex (opposite the teeth), curving inward to a notch which separates the irregularly
convex base. Several stride pass obliquely from the upper teeth to the posterior border.
The posterior hooks are somewhat less and the curves of the posterior outline and base
slightly vary. The foregoing hooks differ from those of the Mediterranean species, which
have a process on the edge of the base beneath the main fang (Plate CXX VI, fig. 1 b), and
the curvatures also differ. If this form represents Savigny’s L. medusae then the British
species should be called L. Montagui.
The tube of Loimia medusae, Sav., is comparatively short, composed of grains of sand
and fragments of shells. Gravier found the longest to be 15 cm., and the diameter
8—9 mm. The tube of the British species is probably similar.
Most of the older authors, such as De Blainville,1 refer to Savigny’s species. It is
doubtful if Montagu’s Terebella constrictor refers to the present form, yet this careful
observer could scarcely have overlooked so fine a southern species as the present.
C. Gravier2 describes interesting, variations in the young examples of Loimia
medusae, Sav., in which the first and second segments differ, and the third has a lobe which
disappears in the adult, the branchige are less finely ramose at the tip, and the hooks,
instead of having the teeth on the crown in a single row, have them double. It is
possible, however, that there may be allied forms which show these distinctions, for even
in Arenicola, to which the able French author alludes, friction will account for many
of the changes between the hooks of the young and those of the old.
Genus CXLVII.—N icolea , Malmgren, 1865.
Scione and Axionice, Malmgren; Physelia and Heteropliyselia, De Quatrefages.
Cephalic collar small, with a row of distinct eyes behind it, the anterior border
forming a spout-shaped arch over the mouth. Body typical. Branchige two, attached
to the second and third segments, the anterior being the larger, dichotomously divided
with short terminal branches. Sometimes a third pair of branchige. Fifteen to seventeen
setigerous processes, the first behind the second gill on the fourth segment; the bristles
have narrow wings on the long and finely tapered tips; no shorter series occurs in
the tufts. A short cirrus in males over the fascicles of bristles in the third and fourth
segments: none in females.3 The avicular hooks commence on the second setigerous
segment, (fifth) uniserial at first, then at seventh biserial for seven segments, afterwards
uniserial. Ventral scutes conspicuous. The anterior nephridia are a little less than
the posterior. Tubicolar.
1 f Diet. Sc. Nat. Vers, et Zooph./ pi. v, fig. 1.
3 e Nouv. Arch. Mus. Paris/ 4® ser., t. viii, p. 224, with text-figs. 396—399.
3 A rather thick cirrus over the bristles of the fourth and fifth segments occurs in N. zostericola
and N. venustula from Plymouth, so that there is no difference in this respect. The processes were
larger in the small N. zostericola than in the adult N. venustula. Allen says Crawshay gives
N. venustula seventeen pairs of bristle-tufts, whereas in N. zostericola there are fifteen. Fauvel gives
N. venustula fifteen to seventeen pairs of bristles and states that the two forms belong, to one species.
Tauber found three pairs of branchiae and sixteen to seventeen bristle-tufts in N. zostericola, and
Leuckart, in this form, describes three pairs of branchiae and fifteen bristle-tufts.