Chapter XVIII: Introduction (14)

_Parietes_: their internal surface is very strongly ribbed
longitudinally, the ribs being coarsely denticulated at their bases,
and finely fluted along their sides. The sheath is transversely
ribbed, and clothed with an epidermis furnished with transverse
rows of fine hairs. The _radii_ are of a dead white, whereas the
parietes are translucent; the summits are parallel to the basis;
they are broad; the radii of the carino-lateral compartments appear
extraordinarily broad, owing to the narrowness of the parietal
portion: the sutural edges are furnished with coarse septa, which
are sinuous, irregular, and obtusely denticulated; the interspaces
are filled up solidly. The _alæ_ are thin, with their sutural edges
almost smooth, and their summits oblique: in some specimens, during
the diametric growth, a mere, almost thread-like ribbon is added
to their sutural edges. _Basis_ slightly cup or saucer-shaped;
moderately thick, permeated by fine pores, and generally ribbed in
lines radiating from the centre. The walls and basis adhere together
very firmly.

_Mouth_: labrum with six teeth: mandibles with five teeth; the three
upper teeth being sharp, narrow, and unusually prominent; the two
lower teeth minute and sharp; maxillæ without a notch. _Cirri_ much
injured: first pair with one ramus apparently one third longer than
the other: segments not very protuberant: the posterior cirri have
elongated segments with five pairs of spines.

_Affinities._--This species is very distinct from all the foregoing:
in the carino-lateral compartments being so narrow, and tending, as
we may suppose, to become aborted; in the form and structure of the
whole shell, and in its habits, this species shows an affinity and
passage to the coral-inhabiting sub-genus Creusia, which has only
four compartments. There is also a close affinity to the sub-genus
Acasta. This species is so closely allied to the following, that
I at one time felt some doubts whether they ought to have been
specifically separated; it is also probably closely allied to _B.
terebratus_, but the materials hardly suffice for judgment: it is
also related, though less obviously, to _B. vestitus_.

35. BALANUS CEPA. Pl. 7 fig. 8 _a_-8 _c_.

_Shell dirty reddish-purple, steeply conical: radii narrow: basis obscurely porose. Scutum with the lines of growth crenated: tergum with the spur truncated, broad as half the valve, and depending beneath the basi-scutal angle as much as half its own breadth._

_Hab._--Japan, attached to an Isis, Mus. Cuming. Attached to an
oyster, Mus. Stutchbury.

As already stated, this species comes in all essential respects very near to the last, though differing much in appearance; I have seen two sets of specimens, and two sets of _B. allium_, and there was no variability or passage in the points in which they differed; hence I must consider them as specifically distinct.

_Shell_, steeply conical, strongly but bluntly ribbed longitudinally;
coloured either all over dull reddish purple, or with the upper part
only pinkish purple: in one set of specimens, the yellow epidermis
was partially persistent. Radii narrow. Orifice small, ovate. The
wall of the carino-lateral compartment is very narrow. The internal
surface of the parietes is ribbed, but finely, and only in the lower
part. The septa, on the sutural edges of the radii, are finer than in
_B. allium_. Basis flat, obscurely permeated by pores. The largest
specimen is .25 of an inch in basal diameter.

_Scuta_: these are longitudinally and finely striated; the
basi-tergal corner is more rounded off than in _B. allium_, and the
articular ridge is not nearly so prominent: internally, the adductor
ridge is rather more prominent. The _Tergum_ is rather broader: its
apex is produced into a minute sharp point: the scutal margin is
straight; the spur is broader, and measured from the basi-scutal
angle of the valve, considerably longer; namely, as long as half
the width of the basal margin of the spur, whereas in _B. allium_
it is only about a quarter as long as the basal margin of the spur:
the lower edge of the spur is not here so directly transverse to
the longitudinal axis of the valve as in _B. allium_: the external
surface is not so flat as in that species, and a depression runs down
to the basi-scutal angle of the spur.

Considering the difference in the shape and appearance of the shell, with its narrow radii and small orifice; considering the less strongly ribbed internal lamina of the parietes, the finer septa on the sutural edges of the radii, the slight difference in outline in the scuta and terga, more especially the greater length of the spur, I conceive I am right in ranking this form as a distinct species, though assuredly it is very closely allied to _B. allium_, and even still closer to the following _B. quadrivittatus_.

36. BALANUS QUADRIVITTATUS. Pl. 8, fig. 1.

_Shell steeply conical, having four longitudinal gray bands placed crosswise: radii with their summits oblique: basis thin, solid. Scutum, with the lines of growth smooth; no distinct pit for the lateral depressor muscle: tergum as in B. cepa._

_Hab._--East Indian Archipelago, attached to lamelliferous corals,
and associated with _Pyrgoma grande_ and _Creusia spinulosa_, Mus.
Brit. and Stutchbury and Darwin. Philippine Archipelago, attached to
a Tetraclita, Mus. Cuming.

I have seen four sets of specimens of this species, taken in four different places, one set containing above twenty individuals, and all resembled each other exactly: nevertheless, this species comes so close to _B. cepa_, that I am somewhat doubtful about its specific distinctness.

_General Appearance._--Shell smooth, or slightly folded, steeply
conical; white, with four longitudinal bands of pale brownish-gray
colour, namely, on the rostrum, the carina, and the two lateral
compartments: the carino-lateral compartments are very narrow and
almost white: the four brownish-gray bands are darkest in the upper
part of the shell, though always rather faint, and die out towards
the base: they can sometimes be seen to be formed of several narrow
longitudinal stripes; the tint shows a trace of containing purple.
The orifice of the shell is small, rhomboidal, and not quite entire,
owing to the obliquity of the summits of the moderately broad radii.
In structure, the shell, radii, and alæ resemble those in the last
species. The basis, however, does not appear to be permeated by
pores. Basal diameter of largest specimen .25 of an inch.

The _Scuta_ most closely resemble those of _B. cepa_, but the lines
of growth are not crenated, and internally there is only a very
minute pit for the lateral depressor muscle, placed almost on the
edge itself of the valve. The _Tergum_ hardly differs at all from
that of _B. cepa_, but is perhaps of rather greater breadth.

The _Mouth_ does not differ from that in the last two species. In the
_Cirri_, the three posterior pairs have elongated segments, bearing
only three pairs of spines, of which the lowest pair is minute: in
_B. allium_, and I believe in _B. cepa_, there are five pairs of
spines on each segment.

This species differs from the last only in the peculiar colouring, smoother walls, more oblique radii, solid basis, and more especially in the scuta having the lines of growth not crenated, and internally, in the pit for the lateral depressor muscle being so very minute and placed on the basi-tergal edge of the valve. The posterior cirri, also, I believe, differ in the number of the spines which the segments support; nevertheless, I cannot feel confident about the specific distinctness of _B. quadrivittatus_.

37. BALANUS TEREBRATUS. Pl. 8, fig. 2 _a_-2 _b_.

_Shell white, strongly ribbed longitudinally, with the basal margin produced into long points: basis concave, not permeated by pores, but strongly ribbed externally in radiating lines; the interspaces between the ribs being riddled by minute rounded apertures, often placed in double rows._

_Hab._--Unknown, Brit. Mus., attached to a lamelliferous coral.

I have in this instance broken through my rule of not describing a Cirripede without examining the opercular valves; but the species here named is so peculiar, that it would have been a fault to have passed it over. There is but a single specimen in the British Museum, without, as just stated, the operculum, and of course without the animal's body.

_Shell_, white, depressed, conical, somewhat elongated in its
rostro-carinal axis; orifice rather small, pentagonal, toothed,
elongated. Parietes rather thin, with extremely prominent
longitudinal ribs, produced at the basal edge into long spikes: the
internal surface is also ribbed, but less strongly than the outside.
Radii rather narrow, with oblique, not smooth summits; sutural edges
very finely and obscurely crenated. Alæ with their summits extremely
oblique. Lower edge of sheath closely attached to the walls. The
carino-lateral compartments are rather narrow.

_Basis_, slightly concave or saucer-shaped; the circumference
is produced into long spikes, corresponding with those on the
basal margin of the parietes: these projections equal half the
semi-diameter of the shell. The internal surface of the basis has
slightly prominent, rounded ridges; and the external surface has
extraordinarily prominent, sharp ridges, radiating from the centre;
the edges of the external ridges are irregular, notched, and knobbed.
I have seen in no other species external ridges on the basis or
surface of attachment; and what is more remarkable, the interspaces
between the ridges are penetrated by small rounded apertures, of
irregular shape and unequal sizes; and these are generally arranged
in an irregular double row, and externally are closed by the
membrane, which clothes the basis. In the sub-genus Acasta, the basal
cup is sometimes penetrated by similar holes, but these seem never
to extend over the whole basis, and are very variable; nevertheless,
in some specimens of _Acasta spongites_ from the Cape of Good Hope,
portions of the basis closely resembled, except in the absence of
the radiating ridges, the structure here described, but the holes
were not arranged in any definite order. The internal surface of
the parietes in _Acasta sporillus_ presents a somewhat analogous
appearance, but the pits do not penetrate through the walls. This
species, I have no doubt, is closely allied to the sub-genus Acasta,
and to _Balanus navicula_ with its allies, and, but much less
closely, to _B. allium_ with its allies. Indeed, had _B. terebratus_
inhabited a sponge, I should have been compelled to have ranked it in
the sub-genus Acasta.

38. BALANUS VESTITUS. Pl. 8, fig. 3 _a_-3 _b_.

_Shell pinkish-purple or white, clothed by an orange-coloured membrane; radii represented by mere fissures; basis solid. Scutum, with a sharp, curved adductor ridge; with crests for the lateral depressor muscle: tergum, with the spur short, truncated, one third of width of valve._

_Hab._--New Zealand, New South Wales, Mus. Brit. and Stutchbury;
attached to shells.

_General Appearance._--Shape conical, often steeply conical; orifice
small; radii not developed, represented by mere fissures. The walls
are smooth, or slightly, or strongly ribbed longitudinally. The shell
itself is of a fine peach-blossom pink, or nearly white, but it is
generally covered by a thick yellow or brownish-orange epidermis.
Opercular valves pinkish, but similarly covered. Basal diameter of
largest specimen .7 of an inch.

_Scuta_, with the lines of growth closely approximate; surface
somewhat convex. Internally, the articular ridge is very little
prominent, but runs far down the tergal margin; in some specimens,
however, it is shorter and more prominent. The adductor ridge is
strongly prominent, is curved towards the rostral angle, and runs
down nearly to the basal margin. The rostral depressor muscle is
lodged in a small cavity, formed, as usual, by the overlapping of
the occludent margin; within this cavity there are either tolerably
distinct little crests, or merely traces of them, for the attachment
of the muscle. The lateral depressor muscle is attached to several
quite distinct crests, seated in a concavity beneath the adductor
ridge. _Tergum_ rather narrow, with the apex produced or beaked; the
beak is purplish and flat. There is a slight rounded longitudinal
furrow, or depression. The spur is fully one third of the width of
the valve: it is short, with the end truncated, and placed close to
the basi-scutal angle; the basal margin on the carinal side slopes
gently towards the spur. Internally, the scutal margin is scarcely at
all inflected, and the articular ridge is very little prominent: the
crests for the tergal depressores are pretty well developed.

From the points here enumerated, it is clear that the opercular
valves are articulated together much less strongly than is usual with
most species, excepting _B. allium_ and its allies. It is remarkable
that in this species the terga are united to the sheath, not, as is
usual, by a single opercular membrane, but by five or six, one above
the other, the upper membranes not having been exuviated as each new
lower one was formed. The minute spines on the membrane lining the
sheath are rather larger and more numerous than is usual, and to the
base of each spine a tubulus of unusual diameter runs, imbedded in
the shell.

The _Walls_, internally, have unusually numerous, narrow,
approximate, strongly prominent, longitudinal ribs, denticulated at
their bases, and inserted into the furrows on the borders of the
basis: in old specimens these internal ribs die out in the upper
part of the walls. The _Radii_ are not developed in any of the many
specimens which I have seen, and the edges of the compartments on
both sides of each suture are equally marked by slight, irregular
ridges or knobs, answering to the septa and their recipient furrows,
in the species with ordinarily developed radii. There is very little
diametric growth, the orifice being gradually enlarged by the
disintegration of the upper ends of the walls; the _alæ_, however,
in some specimens, do grow a little along their lateral or sutural
edges, so that some little diametric growth must be effected. The
summits of the alæ are very oblique; their sutural edges are plainly
crenated. The sheath descends about half way down the walls. The
_Basis_ is flat, not permeated by pores, but deeply furrowed in lines
radiating from the centre.

_Mouth_: labrum sometimes with no teeth, sometimes with four minute
teeth; mandibles with four teeth, of which the third is blunt and
rather large; the fourth is a mere knob. Maxillæ; there is, as usual,
an upper pair of large spines (beneath which there is sometimes
a small notch), but all the lower spines, instead of standing as
usual in pairs, form a single row. _Cirri_; first pair with the rami
remarkably unequal in length, one ramus having twenty-two segments,
and being more than twice the length of the other, having only nine
segments: these segments, and likewise those of the second and third
pairs, have an inverted conical shape; and they are all less thickly
clothed with spines than is usual. The second pair is short, about as
long as the shorter ramus of the first pair, and has ten or twelve
segments. The third pair is above twice as long as the second pair,
and contains twenty-four segments: this very unusual length is owing
to the presence of numerous thin tapering upper segments, unlike
those generally found in _Balanus_, in the third pair of cirri, and
apparently serving as feelers. These upper tapering segments are
of an inverted conical shape, and support on their upper margins
two very small tufts of spines, one behind and one in front: on the
segments lower down these tufts increase in size, and the spines are
more spread out, so that in the basal segments, the tufts in front
form on the upper margin two or three crowded rows of bristles. The
three posterior pairs of cirri have elongated segments, which bear
on their upper half three pairs of spines; of these the lowest pair
is minute, and the middle pair is only one third of the length of
the upper pair. The sixth cirrus, in the same individual as before,
contained twenty-seven segments in each ramus, that is only three
more than in the third cirrus! I must observe, that the cirri in
all the specimens were irregular, often distorted and monstrous;
and therefore, probably, there is considerable variation in the
proportional numbers of the segments in the cirri.

At the base of the penis there is a minute, knife-edged, triangular
projection. The branchiæ are rather narrow, pointed, and not very
large.

_Affinities._--This is a very distinct species, as shown by the
peculiarities in the cirri, by the absence of radii to the shell,
and by the presence of crests for the attachment of the lateral
scutal depressores. With the exception of this latter character, the
opercular valves clearly show, that _B. vestitus_ is allied to _B.
allium_, _cepa_, and _quadrivittatus_. In some respects this species
manifests an affinity to _B. imperator_, which latter has its third
pair of cirri nearly similar to those of _B. vestitus_.

39. BALANUS IMPERATOR. Pl. 8, fig. 4 _a_-4 _c_.

_Shell internally imperial purple; parietes thick, with their internal basal edges rough with irregular points and ridges; radii narrow; basis very thin, solid. Scutum, with crests for the rostral and lateral depressor muscles; tergum, with the end of spur rounded._

_Hab._--New South Wales, Sydney, Port Stephens, Moreton Bay; attached
to sandstone-rocks and shells, at low-water line; Mus. Brit., College
of Surgeons, Cuming, Stutchbury.

_Shell_ conical, very thick and very strong; longitudinally sulcated
more or less strongly; whole thickness of shell beautifully coloured
rich violet, or more strictly "imperial purple;" externally the
surface, from disintegration, is generally whitish; internally
the colour is best developed: the narrow radii and the thin basis
are white. The largest specimen which I have seen was one and
three-quarters of an inch in basal diameter, the walls close to the
basis being, in this instance, actually .3 of an inch in thickness.

_Operculum_ thick and strong, covered by yellowish-brown epidermis;
internally, the shelly substance is either all of the richest
purple or yellowish-white, tinged, especially in the upper part,
with purple. _Scuta_, with the apex beaked and somewhat reflexed;
articular ridge very thick, little prominent; articular furrow very
narrow, the impression made by the adductor muscle is seated very
high up the valve; there is hardly an adductor ridge, but the surface
of the valve is angularly prominent in a curved line, running from
the articular ridge to near the rostral angle of the valve. At the
rostral angle, the occludent margin is not folded inwards, as is
generally the case, but the surface is flat, and is marked by four
or five crests for the attachment of the rostral depressor muscle.
There are other crests for the lateral depressor muscle. _Tergum_,
with the apex somewhat produced and beaked, but blunt; longitudinal
furrow shallow; spur of moderate breadth, with its lower end rounded;
the basal margin on the carinal side of the spur slopes towards it.
Internally, articular ridge moderately prominent. Crests for the
tergal depressor well developed.

_Parietes_, solid, thick, with the basal internal edge (4 _c_) formed
of short ridges, or flattened and irregular points, which in very old
specimens are but little prominent; inner surface, finely, closely,
and irregularly ribbed longitudinally, but in some specimens nearly
smooth. The _radii_ are nearly white; they are narrow, sometimes
hardly at all developed, and have their summits very oblique and
jagged; exteriorly, they are sulcated in a transverse direction, and
sometimes form oblique steps, from having been formed layer over
layer: their sutural edges are formed of irregularly branching crests
or septa. The _alæ_ have their summits very oblique; their sutural
edges are thick and crenated: the part added during diametric growth
on the inner surface is smooth, and has a different appearance from
the transversely ribbed portions of the sheath, of which the alæ
form a portion. The lower edge of the sheath is hollow beneath. The
carino-lateral compartments are very narrow.

_Basis_ calcareous, thin, white, sometimes opalescent, apparently
formed by an aggregation of very minute calcareous beads, with no
trace of furrows radiating from the centre.

_Mouth_: labrum hairy, with apparently some very minute teeth;
mandibles, with the fourth and fifth teeth small and rudimentary;
maxillæ rather broad, with a narrow and rather deep notch under the
two great upper spines: outer maxillæ with the lower lobe very large.

_Cirri_: first pair, with the rami unequal by several segments:
second pair, with the rami unequal in length by about six segments:
third pair elongated, with the segments very numerous, almost
equalling those in the sixth cirrus; upper segments of both rami much
elongated, each with only a circle of spines; segments in the above
first three pairs of cirri only slightly protuberant. Posterior cirri
elongated, with the upper segments bearing three pairs, and the lower
segments four pairs of main spines, between which there is a small
intermediate tuft.

_Affinities._--This noble Balanus, in all the characters derived
from its opercular valves, and from its cirri, is closely allied to
the last species: in the structure, however, of the shell and of
the basis, it comes closer to the following, _B. flosculus_. The
crests on the under side of the scutum, for the lateral depressores,
are confined to these three species; and the crests for the rostral
depressores are confined to _B. imperator_ and _vestitus_, but they
are generally rudimentary in the latter. The internal basal structure
of the parietes is singularly like that of _Chelonobia caretta_,
though there is no other special affinity to that genus. In the
nature of basis; in the structure, to a certain limited extent, of
the walls of the shell; in the narrowness of the carino-lateral
compartments; in the elongation of the third pair of cirri; in the
crests for the rostral and lateral scutal depressores, _B. imperator_
comes nearer to the genus _Tetraclita_ than does any other species of
Balanus.

40. BALANUS FLOSCULUS. Pl. 8, fig. 5 _a_-5 _f_.

_Shell purple or dirty white, with the internal basal edges of the parietes rough with irregular points and ridges; radii narrow or absent; basis excessively thin, in appearance absent. Scutum with crests for the lateral depressor muscle; tergum very narrow, with the spur pointed._

_Var._ sordidus. (Pl. 8, fig. 5 _b_) _shell globulo-conical, dirty
white, with numerous sharp, narrow, longitudinal folds or ridges_.

_Hab._--Peru and Chile; generally attached to the _Concholepas
Peruviana_, or to _Balanus psittacus_, and associated with
_Chthamalus scabrosus_. _Var. sordidus_, inhabits Tierra del Fuego,
attached to littoral shells, wood, and rock, associated with _Ch.
scabrosus_.

_General Appearance._--Shell either extremely much depressed and
irregular, or globulo-conical, or more rarely cylindrical and
elongated. Walls, either with a few rather broad, smooth, irregular,
longitudinal folds, or, in _var. sordidus_, with numerous sharper
and more prominent longitudinal ridges; basal margin very sinuous.
Colour, either fine rich peach-blossom purple, or so pale as to be
almost white; or in _var. sordidus_ dirty white, generally stained
greenish from confervoid matter. Orifice small, oval, entire. Radii
very narrow, white, or not at all developed, and with even the
sutures not distinguishable. The purple coloured varieties, with
the narrow white radii, the small oval orifice, and folded walls,
have a very pretty appearance, which is far from the case with _var.
sordidus_. The largest specimens attained a basal diameter of .6
of an inch, but this is an unusual size: I have seen a cylindrical
specimen of _var. sordidus_ one inch in length.

The opercular valves are united to the sheath by unusually strong
membrane: internally, their upper parts are stained purple. _Scuta_,
these vary considerably in breadth, some being even broader than in
Pl. 8, fig. 5 _c_, and others as much elongated as in fig. 5 _d_:
these latter come from an elongated cylindrical shell. The valve
externally is unusually convex: the apex, also, projects freely to
an unusual degree. Internally, the articular ridge is moderately
prominent: the adductor ridge is prominent and much curved: in the
upper part it either lies close to, or at some little distance from
the articular ridge. The lateral depressores are attached to several
little crests, occupying a cavity, (often bordered above by a little
ridge) close beneath the adductor ridge. _Tergum_, extraordinarily
narrow and elongated; beak triangular, purple: a longitudinal furrow
runs down the valve: spur narrow, long, bluntly pointed, lying close
to the basi-scutal angle of the valve: the scutal margin is nearly
straight and parallel to the spur. Internally, the articular ridge
is prominent: the crests for the depressores are moderately well
developed: the upper part of the valve is marked by a purple patch,
bounded on one side by the articular ridge, and on the other side
by a very slight special ridge. There is some variability in the
narrowness of the whole valve, and in the sharpness of the spur.

_Parietes._--The under surface, in the more depressed varieties, is
roughened in a remarkable manner nearly or quite up to the sheath,
with very irregular, projecting, and branching ridges, and sometimes
with depending points. These ridges and points are granulated on
their under surfaces. The roughened surface in the more conical
varieties is confined to the basal inner margin. This structure is
nearly the same as that in _B. imperator_, represented (Pl. 8, fig.
4 _c_), but the little ridges are here more apt to be concentric,
instead of radiating. The lateral edges of the compartments on the
inside, especially the carinal edges, project inwards beyond the
inner surface of the shell. The sheath is but little hollow on its
under side. The diametric growth of the shell seems to be quite
capricious; in the same group, some individuals thus increasing, and
others not at all. When the radii are developed they are narrow and
white, with their upper margins nearly if not quite parallel to the
basis: their sutural edges are formed by large, irregular, branching
teeth or septa. The _alæ_, also, have their sutural edges coarsely
crenated; and when the shell increases by diametric growth, they are
added to above the opercular membrane, so as to be nearly square at
top.

_Basis._--When a shell is removed from the surface of attachment,
and inspected even under a lens, there appears to be no basis
whatever, either adhering to the shell, or to the supporting surface:
but when a more careful examination is made, with a higher power,
an excessively thin, translucent, calcareous, irregular layer, or
rather film, can almost always be discovered. This would be more
easily distinguished if the specimens had adhered to rock instead of
to the rugged shells of molluscs. At one time I thought the basis
was partially membranous, for I have certainly scraped off small
fragments of membrane from the supporting surface; but these, when
examined under the compound microscope, seemed always to consist of a
thin sheet of the yellow cementing tissue; and in some instances, a
brittle film of shell, representing the true basis of the cirripede,
still adhered to the upper surface of the membranous bits of cement.
Nevertheless, so imperfect is the calcareous basis, that I should not
be surprised if portions of a true membranous basis did really in
some cases exist.

_Mouth_: labrum with the notch wide, generally with a few little
teeth; mandibles with three teeth, and some inferior knobs; maxillæ
notched. _Cirri_, first pair with one ramus shorter by three segments
than the other ramus. Second and third pairs short, of nearly
equal length, thickly clothed with spines; segments very little
protuberant. Posterior cirri, having elongated segments, supporting
seven pairs of spines.

_Var. sordidus._--This form is very common on the tidal shores of
the Strait of Magellan, and of the southernmost parts of Tierra del
Fuego, near Cape Horn: it lives attached to rocks, mytili, and logs
of wood, and is associated with _Chthamalus scabrosus_. It almost
certainly is the most antarctic form of the genus Balanus. If I were
guided by external appearance alone, I should certainly separate
this form specifically from _B. flosculus_, but, as will be seen in
the following description, the differences consist only in _var.
sordidus_ being much duller and rather differently coloured, in the
longitudinal folds being sharper and more prominent, and in the whole
shell being rather more globular, and on an average rather larger;
but in the true _B. flosculus_ there is considerable variation in
all these respects, as there likewise is in _var. sordidus_; thus
some of the cylindrical varieties of the latter have less prominent
ridges than even _B. flosculus_. In general appearance I have seen
some _nearly_, but not exactly, intermediate forms; therefore, I do
not feel positive that these forms may not be specifically distinct,
but have failed, after careful examination, to find any sufficient
diagnostic _characters_. Moreover, in the case of _Balanus lævis_,
I was led to believe that there is an equal and somewhat analogous
amount of variation in the specimens inhabiting Tierra del Fuego and
northern Chile; and in this case I was enabled to show the existence
of strictly intermediate forms in the intermediate districts.

The shell in _var. sordidus_ is generally globulo-conical, dirty
white, frequently with a green tinge, from the growth of confervoid
matter. Orifice small. The exterior surface is covered with numerous
prominent, narrow, sharp ribs or folds, the basal margin being
serrated with projecting points where the folds terminate. When
the radii are not developed, the sutures are very often obscure.
Internally, the shell is faintly tinted of a port-wine purple. In
all points of structure this form is identical with the true _B.
flosculus_. In some few specimens the whole exterior surface was
disintegrated and smooth; and this is generally the case with the
upper parts of the shell. Some other specimens, which had grown
crowded together on wood, had become cylindrical, and consequently
the orifice was as large in diameter as the shell, namely, half an
inch: in some of these cylindrical varieties the sheath was entirely
soldered to the walls. The largest specimens which I have seen were
.6 of an inch in diameter; and above one inch in height.

_Affinities._--This species, in its opercular valves, even in such
trifling characters as the strength of the opercular membrane,
and in its cirri, approaches closely to _B. cariosus_. We even
see on the under side of the scutum, in that species, a single
little ridge, foreshadowing, as it were, the crests for the lateral
scutal depressores, so remarkable in our present species. In the
structure of the shell and of the basis, _B. flosculus_ is much
more closely related to the last species, or _B. imperator_. If it
had been possible to have arranged the species in a single line,
_B. flosculus_ ought undoubtedly to have been placed between _B.
cariosus_ and _imperator_.

41. BALANUS BISULCATUS. Pl. 8, fig. 6 _a_-6 _c_.

BALANUS SULCATINUS (?) _Nyst_, apud D'Omalius (sine descript. aut
tabulâ), Geologie de Belgique, 1853.[100]

[100] I am indebted to M. Bosquet for a specimen, bearing this
name and reference, found in the 'Systeme Bolderien' of Dumont,
(miocene according to Sir C. Lyell) at Bolderberg. The specimen
consists of a rostrum, with a portion of the base attached; and as
these parts are in some degree characteristic, I fully believe this
specimen to be the _B. bisulcatus_. I hope hereafter to give in
the Palæontographical Series fuller illustrations of this and the
following fossil species.

_Radii with their upper margins oblique and smooth; sutural edges smooth: basis permeated by large pores. Scutum narrow, with from two to four longitudinal furrows: tergum with the spur very short, broad as half the valve._

_Var._ plicatus, _with the walls deeply folded; radii narrow, with
their upper margins very oblique_.

_Fossil_ in Coralline Crag, Ramsholt, Gedgrave, Sutton; Mus. S. Wood,
Bowerbank, J. de C. Sowerby. Rauville, dans le Cotentin, Mus. G.
B. Sowerby. _Var. plicatus_, Coralline Crag, Sutton, Mus. S. Wood.
Bolderberg, near Hasselt, Belgium, Mus. Bosquet.

_General Appearance._--Shell conical or tubulo-conical, often rather
globose; walls frequently thin, either very smooth, or deeply
plicated longitudinally: occasionally the same specimen is smooth
in the upper part, and strongly plicated in the lower. The Radii in
the larger specimens are wide, and with their upper margins only
slightly oblique; in the smaller, they are narrower and much more
oblique, but in each case their upper margins are smooth and slightly
bowed. Colour apparently originally nearly white, but with the alæ
generally, in the smaller specimens, clouded with a dark tint:
the radii are usually striped feebly in longitudinal lines. Basal
diameter of largest specimen .8 of an inch; but this seems to have
been an unusual size.

_Scuta_: narrow, with the basal margin forming an unusually small
angle with the occludent margin; surface slightly convex, with lines
of growth approximate, moderately prominent; on the tergal half
of the valve, two distinct rather broad furrows, with sometimes a
third, and even a fourth, nearer to the occludent margin (Pl. 8,
fig. 6 _a_), extend from the apex down the valve, and give it a very
peculiar appearance: the furrows near the tergal margin are the
deepest. Internally, the upper part of the valve is roughened with
small points: the articular furrow is unusually wide: the articular
ridge is very prominent and but little reflexed, with the lower end
almost abruptly cut off: the adductor ridge is prominent, but short:
there are small deepish pits for the rostral and lateral depressores.

_Terga_ (6 _b_), broad, flat, with a slight narrow prominent rim
along the scutal margin, which margin is slightly bowed. The basal
margin on the carinal side of the spur slopes so gradually towards
the spur, that the latter is barely distinct, and is very short, not
depending nearly half its own width beneath the basi-scutal angle: it
is broad, namely, measured across the upper part, as broad as half
the valve; its basal end is obliquely rounded off on the carinal
side; it is placed close to the basi-scutal angle. The carinal
margin of the valve is just perceptibly bowed, and is formed by
rectangularly upturned lines of growth. Internally, the upper part of
the valve is rough; the articular ridge is prominent; the crests for
the tergal depressor muscles are moderately well-developed.

_Parietes_, not porose; internally, the ribs are smooth, with their
basal edges very finely or barely denticulated. The _radii_ (as
already stated) are of variable breadth; they have their upper
margins either very slightly or highly oblique, but always smooth and
rounded: their sutural edges are quite smooth, or sometimes, with
a strong lens, traces of transverse striæ, representing septa, can
just be discovered. The _alæ_ have their upper margins very oblique;
their sutural edges are, in the large specimens, quite smooth; in the
younger ones, plainly crenated; the recipient furrow being clearly
marked with these teeth. _Basis_ plainly porose.

_Varieties._--It is certain that there are longitudinally plicated
specimens of this species, and that the obliquity of the upper
margins of the radii also varies a little: nevertheless some of the
deeply plicated specimens undoubtedly have a very different aspect
from the ordinary varieties, and do really differ in the sutural
edges of the alæ being crenated, and in the greater narrowness and
obliquity of the radii; but these points are all commonly variable.
I have not seen any large specimens of the variety, _plicatus_, so
as to compare them with the large specimens of the normal form, yet
I can hardly entertain any doubt, considering their agreement in
so many important points, that I have rightly treated these forms
as mere varieties; it is unfortunate that none of the specimens of
the _var. plicatus_ seen by me have had opercular valves, as their
presence would have removed all shadow of doubt.

_Affinities_: this is a strongly characterised species, and nearly
allied only to the following species, _B. dolosus_. The furrows on
the scuta in some degree resemble those on _B. lævis_, but there is
no alliance with that species. It is certain that amongst recent
species, the chief affinity is with _B. Hameri_ and _amaryllis_.

42. BALANUS DOLOSUS. Pl. 8, fig. 7.

_Radii with their upper margins oblique and smooth; sutural edges smooth: basis permeated by large pores. Tergum with the spur not very short, broad as one third of valve._

_Fossil_ in Red and Mammaliferous Crag, England; Mus. S. Wood,
Bowerbank, Lyell, J. de C. Sowerby, Henslow, &c. Mammaliferous Crag,
Postwick, near Norwich, Mus. Lyell.

This species so closely resembles _B. bisulcatus_, both externally and in all the essential characters of the parietes, radii, and basis, that it is quite superfluous to describe over again these parts. The specific characters are derived from the opercular valves, which present well defined distinctions, found by me constant in several specimens of both species. _B. dolosus_, like _B. bisulcatus_, has quite smooth and deeply plicated varieties, often adhering to the same univalve. The ribs on the inner surfaces of the parietes are remarkably prominent. I think the upper margins of the radii are in this species rather more oblique than in _B. bisulcatus_. The sutural edges of the radii are marked by the finest striæ, representing septa. The sutural edges of the alæ are generally distinctly crenated. The basis is often slightly cup-formed, and very plainly porose: its surface is marked by radiating ridges. The orifice of the shell is large, and elongated, especially in young specimens. The basal diameter of the largest specimen is .4 of an inch.

The _Scuta_ have no trace of the two or three longitudinal furrows so
conspicuous on these valves in _B. bisulcatus_, and which, in that
species, run down from the apex of the valve; this fact showing that
the furrows occur in quite young individuals. The whole valve is not
quite so narrow as in _B. bisulcatus_, but otherwise agrees with it
in shape: internally, there is hardly any difference: the articular
furrow is not so wide: the articular ridge is very prominent, and
abruptly truncated at its lower end: the adductor ridge is also
prominent; it here runs a little higher up the valve than in _B.
bisulcatus_. The _Tergum_ differs more in the two species: the spur
is not so broad; measured in its upper part, it is only about one
third of the entire width of the valve, instead of being half as
wide as the valve: it is considerably longer, depending beneath the
basi-scutal angle more than half its own width: the basal margin of
the valve on the carinal side, does not slope so gradually into the
spur: the occludent and carinal margins are slightly arched, as in
_B. bisulcatus_. Internally, the surface is rough, the articular
ridge is prominent, and the crests for the tergal depressores are
well developed,--all as in _B. bisulcatus_. It is remarkable, how
generally the opercular valves have been preserved in this species
in its fossil condition, as compared with most other species of the
genus.

It is not easy to distinguish by external characters the rugged varieties of this species from _B. crenatus_; indeed, the only difference is that the furrows receiving the edges of the radii, generally, exhibit in _B. crenatus_ a slight impression of the septa, which are entirely absent in _B. dolosus_. By internal characters, such as the non-porose parietes, and porose basis, our present species widely differs from _B. crenatus_.

43. BALANUS UNGUIFORMIS. Pl. 8, fig. 8 _a_-8 _b_.

BALANUS UNGUIFORMIS. _J. de C. Sowerby_ (!). Mineral Conchology (sine
descriptione) Tab. 648, fig. 1, (Jan. 1846).

---- ERISMA. _J. de C. Sowerby_ (!). Ib., fig. 2.

---- PERPLEXUS. _Nyst_, apud D'Omalius (Sine descript. vel Tab.),
Geologie de la Belgique, 1853.[101]

[101] I am much indebted to M. Bosquet for specimens bearing this
title, from Klein Spauwen, which certainly appear to me, as far as
can be judged by the separated compartments, without the opercular
valves, to belong to our present species.

_Parietes thin, sometimes permeated by pores; radii with their upper margins oblique; sutural edges very finely crenated: basis solid. Tergum with the spur narrow, bluntly pointed._

_Var._ erisma, _with the walls longitudinally folded or ribbed_.

_Fossil_ in the Eocene formation, Isle of Wight, Colwell Bay;
Hordwell; Barton, (Chama Bed); Headon; Bembridge. Bergh, near Klein
Spauwen, Belgium (?). Attached to various shells and wood. Mus. J. de
C. Sowerby, E. Forbes, F. Edwards, Charlsworth, T. Wright, Bowerbank,
Tennant, Bosquet.

This species, the most ancient one as yet well known in the genus, presents to the systematist a most unfortunate peculiarity, in the parietes being almost as often as not permeated by small pores: I have seen no other instance, except to a limited degree in _B. glandula_, of this character being variable, and hence it must be still considered of high classificatory value, in so varying genus as Balanus. Owing to this varying condition of the parietes, together with the basis being quite solid, our present species has as good a claim to be ranked in the last as in the present section; indeed, I think it has more affinity to _B. crenatus_ and _glandula_ in the last section, than to any other recent forms: I have placed it in its present place, owing to its intimate affinity to _B. varians_, in which the parietes seem always to be solid; and partly, I believe, because all the first specimens examined by me exhibited no traces of parietal pores. Owing to the kindness of Mr. F. Edwards, I have seen the original specimens, excellently figured by Mr. J. de C. Sowerby in the 'Mineral Conchology:' I can perceive no difference between _B. unguiformis_ and _erisma_, excepting that the walls in the latter are longitudinally folded,--a character we know to be variable in so many species. In both varieties, the parietes are sometimes porose and sometimes solid. The smaller specimens, however, figured in the 'Mineral Conchology' to the right hand, may possibly be a distinct species, as I infer from the narrowness of their radii.

_General Appearance._--Shell, tubulo-conical, sometimes considerably
elongated and sub-cylindrical: surface either very smooth, or
slightly folded, or deeply folded so as to be strongly ribbed
longitudinally: orifice rather large, rhomboidal, narrow at the
carinal end, toothed, but not deeply: walls rather thin and fragile:
radii of moderate width, with their summits oblique, not quite
smooth. Basal diameter of largest specimen, about three quarters of
an inch.

_Scuta_, with the external surface smooth: there is a trace of a
furrow running down the valve from the apex, near to the occludent
margin, and this is only worth mentioning from the analogous furrows
in _B. bisulcatus_. Internally, the upper surface of the valve is
roughened: the articular ridge is very prominent, and slightly
reflexed: there is no distinct adductor ridge; there is a slight but
variable depression for the lateral depressor. _Tergum_, with the
longitudinal furrow shallow; spur moderately long, about one fourth
or one fifth of the width of the valve; placed at about its own width
from the basi-scutal angle; basal end bluntly pointed; the basal
margin on the opposite sides of the spur forms a nearly straight
line; the carinal margin has an extremely narrow border formed by
upturned lines of growth. Internally, the surface is roughened with
little points: the articular ridge is prominent: the crests for the
tergal depressores moderately prominent.

_Parietes_: the longitudinal ribs on the internal surface are either
feebly, or, in the lower part, strongly developed; their basal ends
are only just perceptibly denticulated. As already stated, in about
half the specimens, there were no traces of parietal pores; in the
other half there were either distinct or obscure pores; the pores
are circular, generally of unequal sizes, and never large; in the
same individual they would sometimes be almost wholly absent in some
of the compartments, and quite plain in the other compartments. The
Radii are either moderately wide or rather narrow, and have their
upper margins very oblique, and not distinctly arched, and not quite
smooth: their sutural edges are very finely crenated, the teeth or
septa not being denticulated. The upper margins of the _alæ_ are
rather less oblique than those of the radii: their sutural edges are
barely crenated. The _basis_ is thin, and without any trace of pores;
the upper surface is sometimes furrowed in radiating lines.

44. BALANUS VARIANS. Pl. 8, fig. 9.

B. VARIANS. _G. B. Sowerby_, in Darwin's Geolog. Observ. on South
America, (Sept. 1846), Tab. 2, fig. 4, 5, 6.

_Parietes moderately thick: radii with their upper margins very oblique; sutural edges almost smooth, or finely crenated: basis finely porose. Tergum with the spur small, narrow, bluntly pointed._

_Hab._--Port St. Julians, Patagonia; ancient Tertiary formation.
Eastern plain of Tierra del Fuego (?).

This species comes so close to _B. unguiformis_, that I have some doubt whether they ought to be specifically separated: the whole shell is stronger, and the basis can be seen to be porose when a polished section is made: the spur of the tergum is smaller, more pointed and more medial, but these latter differences may be due to mere variation. Should _B. varians_ and _unguiformis_ prove to be the same species, the latter name has the priority.

_General Appearance._--Shell moderately strong and thick; shape
conical or tubular, or even inverted conical; orifice moderately
toothed, large, sub-trigonal; walls either smooth or longitudinally
folded; the elongated specimens are most apt to be smooth. The
Radii are narrow and oblique. Diameter of largest specimen above
three-quarters of an inch.

_Scuta_, with the lines of growth moderately prominent; the internal
surface of the valve has been ill preserved; but a very prominent,
hardly reflexed, articular ridge, can be distinguished, as well
as the absence of an adductor ridge. _Terga_, with no distinct
longitudinal furrow running down the valve: spur short, bluntly
pointed, narrow, about one fifth or one sixth of width of valve;
placed at above its own with from the basi-scutal angle; the
basal margin, on each side close to the spur, curves towards it.
Internally, all that can be distinguished, is that the articular
ridge is prominent.

_Parietes_; their inner surfaces appear to have been nearly smooth;
the absence of parietal pores could be made out only by polishing
a transverse section. The Radii are narrow, and have their upper
margins very oblique and rather smooth: in the elongated varieties
the sutural edge appears to be almost absolutely smooth; in the
conical specimens it is slightly crenated, the septa being apparently
not denticulated. In living species we have a similar variation in
the state of the sutural edges of the radii, in _B. balanoides_ and
_crenatus_ the edges being much smoother in much elongated specimens
than in other varieties. The _alæ_ have their upper margins less
oblique than those of the radii, with their sutural edges barely
crenated. The _basis_ is either flat, or, in the elongated specimens,
deeply cup-formed; in section it can be seen to be finely and
irregularly porose.

45. BALANUS INCLUSUS. Pl. 8, fig. 10 _a_-10 _c_.

_Shell reddish-brown: radii broad, with their upper margins not oblique, or only moderately oblique; sutural edges with plainly denticulated septa: basis porose. Scutum without an adductor ridge; tergum with the spur rather narrow._

_Var._ (_a_) (Pl. 8, fig. 10 _b_, 10 _c_), _with the shell elongated
in its rostro-carinal axis; basis narrow, clasping the stem of a
zoophyte; lateral compartments much broader than the almost linear
rostrum, carina, and carino-lateral compartments_.

_Var._ (_b_), _with rough longitudinally folded walls, and with the
summits of the radii forming an angle of about 45° with the basis_.

_Fossil_ in Coralline Crag, Sutton and Gedgrave; attached to
foliaceous Bryozoa; Mus. S. Wood, Bowerbank. _Var. a_, Coralline
Crag, Sutton, attached to cylindrical branches of corals; Mus. S.
Wood. _Var. b_, attached to shells, Osnabruck, Hanover, Mus. Lyell;
Bünde, Westphalia, Mus. Krantz.

My materials consist of a beautiful series of specimens in Messrs. Wood and Bowerbank's collections; but unfortunately only a single young specimen had its opercular valves preserved. Not one specimen of the very curious variety (_a_) had opercular valves, yet I cannot feel any doubt about its being only a variety, caused by its attachment to a thin cylindrical branch of a coral, instead of to a foliaceous Bryozoon; it will, however, be convenient to give a separate description of this very remarkable form. With respect to var. (_b_), both sets of specimens came to me with the name _B. stellaris_, of Bronn; but as Bronn distinctly states, that in his species the parietes are porose, and as such is not here the case, this cannot possibly be that species: these specimens did not possess their opercular valves, and therefore cannot be identified with certainty.

_General Appearance._--Shell conical, with the orifice rather large,
and rhomboidal. The surface is very smooth, except in var. (_b._)
from the Continent, in which it is rugged and longitudinally folded.
The colour is ochreous-brown (chiefly no doubt derived from the
imbedding substance) tinged with red. The radii often have a much
darker and more distinct red tint; they are sometimes longitudinally
striped with dirty white. The radii are broad, with their summits
straight, and very slightly oblique; in _var. b_, however, they slope
at an angle of about 45°. Basal diameter of largest specimens .6 of
an inch; but this is an unusual size.

_Scuta_ (from a young individual), with the growth ridges little
prominent. Internally the articular ridge is moderately prominent,
with its lower end very obliquely rounded off; there is no adductor
ridge; there is a minute pit for the lateral depressor muscle.
_Terga_, with a slight longitudinal depression extending down to the
spur: spur short, with its lower end almost square or truncated,
about one fourth of width of valve, and placed at about half its own
width from the basi-scutal angle. Internally, the articular ridge is
prominent; the crests for the tergal depressores are feebly developed.

_Parietes_, moderately thick and generally strongly ribbed
internally, without parietal pores. _Radii_, wide, with their upper
margins straight, not smooth or rounded, and very slightly (or, in
_var. b_ moderately) oblique; their sutural edges have well-developed
septa, which are denticulated: the interspaces between the septa
are filled up solidly. The _alæ_ have their upper margins oblique:
they are only slightly, and sometimes not at all, added to above the
level of the opercular membrane: their sutural edges are smooth. The
_basis_ is thin, but plainly porose.

_Var._ (_a_).--With respect to this remarkable variety, any one
would at first think it specifically distinct. The shell is much
compressed, or elongated in the rostro-carinal axis, sometimes to
a great degree; I have seen a specimen .25 of an inch in this axis
and only .1 in its broadest part; but this is a very unusual degree
of elongation. The most remarkable character is the extraordinary
narrowness of the carina, the carino-lateral compartments, and of the
rostrum, compared with the great breadth, especially along the basal
margin (Pl. 8, fig. 10 _b_, 10 _c_), of the lateral compartments.
The radii are of unusual breadth. The tips of the rostrum and of the
lateral compartments are a little arched in, tending to make the
shell somewhat globular. The true basis is extremely narrow (fig.
10 _c_): it is deeply grooved, from clasping the thin, cylindrical
stem of the coral to which it had adhered; and I have seen specimens
in which the opposite edges of the groove had met, a tube having
been thus actually formed. From the grooved basis, and from the
elongation of the shell in the rostro-carinal axis, this species
presents so close a general resemblance to _Balanus calceolus_, and
its allies, that I have seen it in a collection arranged on the same
tablet with a fossil specimen of _B. calceolus_. Notwithstanding
the above several strongly-marked characters, by which this variety
differs from the ordinary form, there is a resemblance in colour and
aspect, which though difficult to be described, made me from the
first suspect that the two were specifically identical. In no point
of real structure is there any difference, excepting that, perhaps,
the pores in the basis are here rather smaller; but this might arise
from the little development of the peculiar basis. Having come to
this conclusion, I was interested by finding a specimen in Mr. Wood's
collection, which had originally fixed itself (judging from the form
of the basis) on a cylindrical stem, but which had subsequently grown
on to an adjoining flat surface; consequently, one side of the shell
presented all the peculiar characters of the present variety, whereas
the other side, at the rostral end, was undistinguishable from the
ordinary form. The unequal development of the rostrum on the two
sides was very striking, and clearly showed how great an effect could
be produced by the nature of the surface of attachment.

This singular variety cannot be considered accidental, in the sense
in which this term may be applied to some varieties: the larva
evidently fixes itself intentionally, in a certain definite position,
on the branch of the coral (when a branch is chosen), exactly as in
the case of _Balanus calceolus_, or _Scalpellum vulgare_. But when
other species of Balani occasionally fix themselves on branched
corals, their position seems to be accidental and unsymmetrical; thus
among the symmetrically elongated specimens of the present species, I
found one specimen of _Balanus bisulcatus_, which had evidently been
attached in an almost transverse position to a branch, and had thus
become much distorted; so, again, I have seen specimens of the recent
_B. amaryllis_ attached irregularly to a Gorgonia, in the midst of
the symmetrically elongated shells of _Balanus navicula_, an ally of
_B. calceolus_.

This variety does not seem to attain so large a size as the ordinary
form.

_Affinities._--This species is allied to the two last described
fossils, namely, _B. varians_ and _unguiformis_, but is perhaps
more nearly related to the recent _B. allium_, an inhabitant of
the Barrier Reef of Australia. The longitudinally folded variety
(_b_) can hardly be distinguished by external aspect, or even
by the opercular valves, from _B. crenatus_; but when the shell
is disarticulated, the porose walls and non-porose basis of _B.
crenatus_, allow of no mistake in the diagnosis of the two species.

2. _Sub-Genus_--ACASTA. Pl. 9.