x, bases of the pedicels of the cirri of the young included
cirripede.
[2 a], Pupa of Lepas australis of natural average size, within a half-inch
wide.
[3], Young cirripede (on a smaller scale than Fig. 2), immediately
after the exuviation of the bivalve-like pupal carapace, the
basal segments of the antennæ, the eye-apodemes and eyes.
The young cirripede has just assumed its proper position
at nearly right angles to what it held whilst packed within
the pupa,—this change of position having been effected by
the opening out or stretching of the deep fold of membrane
(see n, in fig. 2) formed over the eye-apodemes and
eyes, previous to the act of exuviation.
a, the three terminal segments of the antennæ of the pupa, still
remaining cemented, in the same position as before, to the
same piece of wood: the basal, or eye-bearing segment (N,
in fig. 4), has been moulted with the pupal carapace.
c, d, legs and caudal appendages of the pupa, not as yet moulted,
but quite functionless; the external membrane of the
thorax, and that lining the sack of the pupa, are, likewise,
as yet retained, but soon will be cast off.
s, bottom of the sack of the young cirripede, which can now be
easily distinguished.
u′, the peduncle.
x, y, z, primordial valves, composed of chitine:
x, being the scutum;
y, the tergum;
z, the carina.
[3 a], small portion of one of the primordial, non-calcified valves,
much magnified.
[4], ventral surface of pupa; on the same scale, and in the same
semi-transparent condition as in fig. 2.
a, antennæ.
b, limit of sack on the sides in the ventral or lower half of the
pupa.
b′, posterior end of the carapace.
c, d, bristles of the natatory legs and of the caudal appendages,
protruded through the orifice of the carapace.
e, orifice of the acoustic sacks.
m, mouth, with the œsophagus attached to it, obscurely seen
through the carapace; the stomach having been removed.
n, apodemes supporting the eyes.
N, the eye-bearing or basal segments of the antennæ.
o, the second or main segment of the antennæ.
p, the third or disc segment of the antennæ.
v, the fourth or terminal segment of the antennæ.
W, ventral surface, bordered by the edges of the carapace; the
letter stands near the extremity of the œsophagus.
[5], First pair of natatory legs:
f, lower segment of pedicel;
g, upper segment of pedicel;
h, lower segment of ramus;
i, upper segment of ramus;
k, outer ramus;
l, inner ramus of same leg;
r, sternal surface between the first and
second pairs of legs, with singular thickened ridges and folds.
[6], Abdomen with two caudal appendages:
1, first abdominal segment, attached to the posterior thoracic segment;
2, second abdominal segment;
3, third or last abdominal segment;
h, lower segment;
i, upper segment of caudal appendage.
[7], Transverse section of the pupa, close to the eye-apodemes;
these being made to stand more upright than in fig. 2.
The internal organs of the animal have all been removed.
a a a′, section of carapace; from a to a′, on the lower side,
forms the ventral surface, with three longitudinal furrows,
here in some degree opened out.
c, crest of thick membrane on each side, forming the sides of
the lateral furrows.
N, the posterior margin of the eye-bearing segment (see fig. 4)
of the antennæ; the edges of which are hardened and
thickened, and are produced inwards, forming
n, the apodemes, to which are attached the (n′) great compound
eyes.
[8], Terminal portion of an antenna, greatly magnified, seen from
above.
o, part of the second or main segment; an oblique line shows
a line of separation of the upper thinner and lower thicker
membrane;
o′, single spine borne at this segment.
p, disc-segment, bearing seven spines;
p′, an irregular border
of the cement-tissue, believed to have debouched through
the spoke-like minute tubes seen on the disc.
v, terminal segment, projecting almost rectangularly outwards;
v′, most delicate tube or ribbon, believed to consist of
cement-tissue.
ERRATA.
Page
[104], thirteen lines from bottom, for “Balanus elongatus,” read “Balanus
galeatus.”
[105], six lines from bottom, for “Balanus elongatus,” read “Balanus galeatus.”
[174], Since the table on the distribution of the fossil species was drawn up, I
have examined some more specimens, sent me by Mr. Wood, which
show that Balanus concavus and Hameri are found in the Red Crag;
and that Verruca Strömia is found in the Coralline Crag; this will
make the total in the Coralline Crag ten, and in the Red Crag eight.
I should, however, add, that the identification of Verruca Strömia
in the two Crags is a little doubtful, as the specimen was without the
opercular valves.
[235], to Fossil localities of Bal. concavus, add Red Crag (Sutton) Mus. S. Wood.
[255], six lines from the top, Bal. crenatus, I have now seen a single Red Crag
specimen .5 of inch in basal diameter.
[278], to Fossil localities of Bal. Hameri, add Red Crag (Sutton) Mus. S. Wood.
[293], nineteen lines from the top, for “Cotantin,” read “Cotentin.”
[300], ten lines from bottom, for “parieted” read “parietal.”