Chapter XV: Introduction (11)

_Scutum_, with fine ridges radiating from the apex, and with the
lines of growth, crenated: internally, the articular ridge is small,
adductor ridge short and barely distinct: there is a rather deep
and narrow pit for the lateral depressor muscle. The whole valve
is much thinner than in _B. trigonus_, which in most respects it
closely resembles. _Tergum_, with the apex pinkish purple, produced
or beaked, but the beak is not needle-like, as in _B. psittacus_
and its allies, for the carinal margin is perfectly preserved up to
the tip. Externally the valve is nearly flat, for the longitudinal
furrow is very shallow. The spur is about one third of the width of
the valve; its lower end is abruptly truncated: in European specimens
(1 _b_) the whole basal margin, on the carinal side, slopes down to
the spur in a straight line, which, together with the sharpness and
production of the basi-scutal angle of the spur itself, gives to the
whole valve a peculiar appearance: in the specimen (1 _c_) from the
Lagulhas Bank, the basal margin on the carinal side is a little more
hollowed out, but it is quite impossible to doubt about the specific
identity of these specimens: in the West Indian variety (1 _d_) the
basal margin on the carinal side forms a distinct but obtuse angle
with the spur. In all cases the crests for the depressor muscles are
very feebly developed.

The _Compartments_ have their radii developed to a rather varying
degree, with their summits oblique; hence the orifice is toothed:
the sutural edges of the radii have their septa barely denticulated;
the sutural edges of the alæ are smooth. The basis, as with the
other species of this section, is permeated by pores; yet I found
one specimen, from the Cape of Good Hope, with the basis apparently
solid, thus offering a very singular anomaly. In the specimen
imbedded in sponge, the basis, as viewed externally, is concave;
whereas in Acasta, which always inhabits sponges, the basis is highly
convex or hemispherical.

The _Mouth_ and _Cirri_ resemble those of _B. trigonus_, and I can
point out no distinguishing character.

With respect to the variety from the West Indies, I have seen two
sets of specimens differing somewhat in external appearance, one set
attached to a coral from St. Vincent's, and another set to an Avicula
from an unknown locality; at first I described these specimens, with
some hesitation, as a distinct species, and I am very far from sure
whether this would not have been the more correct course, although
I am unable to point out any sufficient diagnostic characters. This
form differs from the ordinary _B. spongicola_, in the walls being
more rugged, stronger, and slightly or deeply folded longitudinally;
in this latter case the shell in external aspect differs much from
ordinary specimens of _B. spongicola_; but this is a variation so
common that I dare not place any reliance on it. The colour is more
purple; the summits of the radii perhaps rather less oblique. In the
scuta the only difference is that the articular ridge seems rather
longer, and the adductor ridge perhaps more prominent: in the terga,
as already remarked, the basal margin on the carinal side does not
slope so straight into the spur. These differences I consider all too
slight to be of specific value. The difficulty in determining the
nature of this variety is added to by its approach to _B. trigonus_
in all those points in which it departs from the ordinary _B.
spongicola_, so that for a short time I was even tempted to consider
both these species as varieties of one form. But until _B. trigonus_
is found with its scutum longitudinally striated, and with its tergum
beaked, it can hardly be confounded with _B. spongicola_; for it
should be observed that when in _B. trigonus_ the rows of little pits
disappear from the scuta, as sometimes happens, though rarely, yet
these valves do not become longitudinally striated.

_Balanus spongicola_ occurs, mingled with _B. tulipiformis_, in the
Mediterranean, and by the external characters of the shell alone
cannot be distinguished from that species; but the striated scuta and
beaked terga suffice to separate them. Again, this species, at the
Cape of Good Hope, occurs mingled with _B. Capensis_, and from the
non-striped young varieties of that species, it can, externally, be
distinguished only by the beak of the tergum not being sharp like a
needle. I have seen a single, perfectly characterised specimen, with
its opercular valves preserved, found by Mr. S. Wood in the Coralline
Crag at Sutton, mingled with _B. inclusus_.

16. BALANUS LÆVIS. Pl. 4, fig. 2-2 _g_.

BALANUS LÆVIS. _Bruguière._ Encyclop. Meth. (1789), Pl. 164, fig.
1.[91]

---- DISCORS. _Ranzani._ Mem. di Storia Nat., 1820, Tab. 3, figs. 9
to 13.

---- COQUIMBENSIS. _G. B. Sowerby_, in Darwin's Geology of South
America (1846), Tab. 11, fig. 7.

[91] M. Deshayes, in his descriptions of the plates, considers this
figure, I have no doubt erroneously, as that of _B. perforatus_, of
Bruguière. The _B. Coquimbensis_ of Sowerby, is a different species
from the _B. Coquimbensis_, of Chenu, 'Illust. Conch.,' tab. 6,
which latter is unknown to me.

_Shell covered by brown membrane, or naked and white or pale purple; orifice small; radii very narrow. Scutum with one or two deep longitudinal furrows._

_Var._ nitidus (fig. 2): _shell not covered by membrane, white or
pale purple: orifice but slightly toothed: scutum generally with two
furrows_. Hab.--Chile, as far south as Concepcion; Peru; California.

_Var._ Coquimbensis (fig. 2 _a_): _with the basal cup partly filled
up with thin, irregular, calcareous layers, making a cancellated
mass_. Fossil, and recent.

_Hab._--Strait of Magellan, ten to twenty fathoms, attached to
shells; often entirely surrounding pebbles, forming globular masses;
associated with _Verruca lævigata_. Chile and Peru, (generally _var.
nitidus_), often attached to _Balanus psittacus_. California. Very
common.

_Fossil_ in an ancient tertiary formation (middle bed) at Coquimbo,
Chile. In a recent deposit (_var. nitidus_) at the height of 1000
feet at Valparaiso; with Human remains at San Lorenzo, Callao, Peru.

I may premise that, having myself collected this species from the same locality, the Strait of Magellan, where no allied species occurs, attached to the same Mytilus and associated with the same Verruca, I feel confident that it is the _B. lævis_ described by Bruguière; and there can hardly be any doubt that it is the _B. discors_ of Ranzani. With respect to the old tertiary specimens from Coquimbo, named _B. Coquimbensis_ by Sowerby, they differ from the recent in no respect, except in being considerably larger; and therefore I cannot consider them specifically distinct. At first I was unwilling to believe that the specimens with a single very broad longitudinal furrow, and those with two rather broad, or with one narrow furrow, on their scuta, could belong to the same species; but I soon found that all these varieties occurred mingled together, and that they differed in no other respect whatever. Generally, however, all the individuals in the same cluster had the same variety of scutum,--thus adding one more to the many instances amongst cirripedes of variations common to whole groups of specimens. Still more unwilling was I to believe that _var. nitidus_ and the common variety could belong to the same species. Their general aspect is totally unlike: _var. nitidus_ has a smooth, clean, naked shell, either white or pale purple, somewhat globulo-conical, often with a nearly entire orifice; whereas the other common variety generally has a more steeply conical shell, with a toothed orifice, and is covered by a dirty brownish membrane. Moreover, though I have seen hundreds of specimens from Tierra del Fuego, I have not seen one specimen of _var. nitidus_, or even of an approach to it in appearance; and, on the other hand, _var. nitidus_ is the common form in Chile and Peru; though I have seen one or two specimens of the membrane-covered variety from Valparaiso. Such facts strongly induced me to believe that these forms were specifically distinct; but upon careful examination I could find no other or more important differences than those just specified. Some specimens from northern Chile are in an intermediate condition; and from Concepcion, in the south of Chile, where the climate approaches in character to that of the more southern parts of the Continent, there are many specimens, in so intermediate a condition that I know not whether or no to rank them under _var. nitidus_. Thus I became convinced that these forms are only varieties. At Concepcion, some few specimens are pale purple, and yet are wholly invested by thick brown membrane, thus uniting the two extreme varieties. From California I have seen both varieties, but I do not know which is most common there. With respect to the great difference in aspect between the specimens from northern Chile and Tierra del Fuego, we shall hereafter see a strictly analogous case in _Balanus flosculus_. Finally, I may add that _B. lævis_ seems to represent in the southern hemisphere and on the west coast of North America, the _B. perforatus_ of Europe and Western Africa.

_General Appearance._--Shell conical, sometimes slightly globular;
surface smooth (that is, not folded), either naked, and in that case
white or pale purple, or covered by dirty yellowish-brown membrane.
Orifice small, more or less toothed, rarely exceeding one third of
the basal diameter. Radii very narrow, often not developed, the six
sutures forming in all cases deep and narrow clefts. The largest
recent, but much depressed, specimen which I have seen (from the
Strait of Magellan) was three fourths of an inch in basal diameter;
specimens growing congregated are often much elongated. I have seen
one with the basal cup between two and three times as deep as the
height of the compartments. Of the ancient tertiary specimens, the
largest had a diameter of three fourths of an inch, and a total
length of actually two inches (fig. 2 _a_); another of these fossils
had a basal cup in depth equalling four fifths of the entire length
of the shell and basis.

The _scutum_ has either one very broad and deep longitudinal furrow
(2 _b_), or two moderately broad and deep (2 _e_), or two narrow and
deep, or less frequently one narrow and inconspicuous longitudinal
furrow (2 _f_); rarely there is not one furrow; sometimes there are
none towards the apex, whilst furrows have been formed in the lower
part of the valve. In young specimens the furrows extend down to
the actual basal margin, but in old specimens they often fall short
of this, and, as a consequence, the furrows become crossed by one,
two, or three calcareous ridges, which ridges at successive periods
formed the basal margin of the valve. The external surface is covered
by yellow membrane; and fragments of several successive opercular
membranes are often attached to the zones of growth.

Internally the articular ridge is not very prominent, but is
remarkable (2 _c_, 2 _d_) from its lower point being produced into a
long, sharp, sub-cylindrical, free style (like the hinge of a common
gate), which is generally broken off in disarticulating the valve
from the tergum. The adductor ridge is either sharp and prominent
or blunt: it extends up the middle of the valve nearly to the apex,
and downwards it trends a little towards the occludent margin. The
pit for the lateral depressor muscle is minute but deep: the basal
margin is sometimes hollowed out under this pit. Sometimes there is
a distinct, but blunt ridge, caused by one of the furrows outside,
parallel to the adductor ridge, and placed between it and the little
pit for the lateral depressor; in this case, the basal margin, as
viewed internally, is rendered sinuous (2 _d_), as is best exhibited
in the great fossil specimens from Coquimbo.

_Tergum_ (2 _g_).--Spur of moderate length and breadth, with its
lower end obliquely truncated and rounded. The longitudinal furrow
has its edges somewhat folded in. The basal margin on the carinal
side of the spur is sometimes a little hollowed out. The crests for
the depressor muscles are well developed; but the corner of the valve
supporting them is extremely thin, and is often imperfectly calcified.

_Compartments._--The parietal tubes are not crossed by transverse
septa, but in their upper parts are filled up solidly. The radii are
always very narrow, with their summits oblique, though to a variable
degree: their sutural edges have fine and closely approximate septa,
with minute denticuli: the sutural edges are received in a furrow, on
the opposed compartment, of unusual depth; hence the lines of suture
run, in the lower part of the shell, almost exactly in the middle
between each two compartments. The alæ are added to above the level
of the opercular membrane.

The _Basis_ is often thick, with an underlying layer, largely
cancellated or honeycombed. When many specimens grow crowded
together, the basis is generally deeply cup-formed, or even
sub-cylindrical; and equals as much as four fifths of the length of
the entire shell. In such cases, in some few recent specimens, and
in all the large or even quarter-grown old tertiary specimens, but
not in the quite young fossil specimens, a structure is presented,
which I have not seen in any other Cirripede, namely, the basis (Pl.
4, fig. 2 _a_) is filled up for one third, or even for more than
half its depth, by successive, separate, calcareous, transverse
layers or septa. It would appear as if the basal cup had grown too
large for the animal's body, and so required filling up. The layers
are thin and fragile; a single layer never stretches across the
whole shell; each is irregularly mammillated or blistered, with the
convex surfaces generally directed upwards; the layers are furnished
on their under sides with little pillars and short ridges, resting
on the layers beneath; it rarely happens that the supports of one
layer lie directly over those of another, though this is sometimes
the case. In a vertical section, the mass formed by these irregular
layers has a coarsely cancellated structure. This structure, although
confined to this one Cirripede, is not so anomalous as might at first
be thought, for in most species of the genus, each time that the
circumference of the basis is added to, an excessively thin calcified
film is thrown down over its whole inner surface; and in any of these
species, if the films had been formed thicker and had rested only
on certain points, instead of over the whole underlying layer, the
cancellated structure above described would have been produced.

_Mouth_: the labrum is either destitute of teeth, or has two or three
very minute teeth. The palpi have a tuft of very long spines at their
ends. The third tooth of the mandibles is thicker and larger than
the two upper ones. The maxillæ have either a nearly straight edge,
or the inferior corner is obliquely truncated, and projects much
beyond the rest of the edge. In the _Cirri_, none of the segments are
very protuberant: in the first pair, one ramus is nearly twice as
long as the other: in the posterior pairs, the segments are not much
elongated, but each supports seven pairs of spines.

_Var. nitidus_: with respect to this variety I have little to add
to my preliminary remarks on its peculiar appearance, owing to its
smooth, naked condition, and pure white or pale purple colour. This
colour, when examined through a lens, is seen to consist of very
fine longitudinal stripes; and is produced by the calcareous matter
within the longitudinal parietal pores being thus coloured. Generally
the scuta have two longitudinal furrows; but I have seen a scutum
of one perfectly characterised specimen with only a single broad
furrow, like that which frequently occurs in the membrane-covered
variety. _Var. Coquimbensis_, as before stated, differs only in its
greater size: the scutum, in the one specimen examined, had two
broad longitudinal furrows; neither it, nor the tergum differed from
certain varieties now found on the coast of Chile.

17. BALANUS PERFORATUS. Pl. 5, fig. 1 _a_-1 _d_; Pl. 4, fig. 3 _a_-3 _c_.

BALANUS PERFORATUS. _Bruguière._ Encyclop. Meth., 1789, Tab. 164,
fig. 12 _infra_.

LEPAS ANGUSTA. _Gmelin._ Syst. Naturæ, 1789.

---- ORE ANGUSTIORE. _Chemnitz._ Vol. viii, Tab. 98, fig. 835.

BALANUS CORNUBIENSIS CONICO ORE MINORE. _Ellis._ Phil. Trans. vol.
50, 1758, Tab. 34, fig. 16.

LEPAS BALANUS ET FISTULOSUS. _Poli._ Test. Siciliæ (1795), Tab. 4,
fig. 5, Tab. 6, fig. 1.

BALANUS COMMUNIS. _Pulteney._ Dorset Catalogue, 1799.

---- ---- _Montagu._ Test. Brit., 1803.

LEPAS ANGUSTATA. _Wood._ General Conchology, 1815, Pl. 6, fig. 5.

BALANUS CRANCHII. _Leach_ (!). (_B. Blainvillii_ in Tab.) Encyclop.
Brit. Suppl., vol. iii, 1824.

---- ---- _Brown._ Illust. Conch., 1827, Pl. 7, fig. 9, 10, and 2d
Edit., Pl. 53, fig. 9-12.

---- PERFORATUS. _Chenu._ Illust. Conch., Tab. 3, fig. 9, Tab. 6,
fig. 15.[92]

[92] I have very little doubt regarding any of these references:
I have no means of ascertaining the priority, within the same
year, of Gmelin and Bruguière, but have given it to the latter,
as _perforatus_ is much the best known specific name. English
conchologists seem generally to suppose that the _B. communis_ of
Pulteney and Montagu is the _B. porcatus_ of this work; but I have
not the smallest doubt that I have given it rightly as a synonym
of the present species; the indistinctness of the compartments,
the multitude of fine ridges, the smallness of the orifice, the
longitudinal furrow on the terga, the colour, size, and habitat,
all given by Pulteney or Montagu, will agree with no other British
species. The _Lepas balanus_ of Poli, which is certainly a synonym
of our present species, has been erroneously considered by several
authors to be the same with the _L. balanoides_ of Poli, which
latter undoubtedly is the _B. amphitrite_ of this work.

_Shell pale purple, or white, or dirty ash-colour; smooth, or, from being corroded, finely ribbed longitudinally; sheath purple; orifice generally small; radii generally narrow or absent. Scutum, internally, with a short minute ridge, parallel and close under the prominent adductor ridge. Tergum with the apex somewhat produced._

_Var._ angustus (_Gmelin_) Pl. 5, fig. 1 _a_: _pale dull purple
or white; orifice small or of moderate size; radii very narrow or
moderately wide, white or pale purple, with oblique summits_.

_Var._ Cranchii (_Leach_) Pl. 5, fig. 1 _b_: _corroded, covered with
fine longitudinal ridges owing to the exposed, filled-up, parietal
tubes; dark dirty ash-colour, with a tinge of purple: radii not
developed, or very narrow with oblique summits; orifice small_.

_Var._ fistulosus (_Poli_) Pl. 5, fig. 1 _d_: _shell cylindrical,
white or dull purple; orifice of moderate size or small; basis deeply
cup-formed_.

_Var._ mirabilis, Pl. 5, fig. 1 _c_: _bright purple; radii white,
very broad, with their summits parallel to the basis; orifice entire,
large_.

_Hab._--Southern shores of England; South Wales; Mediterranean;
Western Africa, southward to Loanda, in 9° S.; West Indies (?).
Generally adhering to rocks at a low tidal level; in one case
attached to the floating _Lepas Hillii_, Mus. Jeffreys.

This is a well-marked species, and in its essential characters does not vary much; but owing to the shell being almost as often white as purple,--to its being remarkably subject to disintegration,--to its often becoming cylindrical,--to the radii being either not at all, or slightly, or moderately, or largely developed, and consequently to the orifice of the shell varying in size, the general external appearance of the different varieties is singularly diversified; but when a series of specimens is examined, it is easy to see how one form passes into another.

_General Appearance._--Shell conical, with the orifice oval,
unusually small, being generally only from one third to half of the
basal diameter; sometimes moderately large; in one single instance as
wide as the basis. Radii, often represented by mere lineal fissures,
or they are narrow, or sometimes moderately wide. Colour pale, dull
purple, sometimes lilac, often passing into a dead pure white: the
same individual will occasionally have one part of its shell white,
and another purple: the purple tint almost invariably is nearly
uniform, or not in stripes. The radii are generally white, when
the whole shell is purple, but sometimes they are pale purple: the
sheath is apparently always coloured of a fine claret-purple, with
the triangular portion of the alæ, added during diametric growth,
generally white, but sometimes purple. The surface is quite smooth,
but very often, especially on the shores of England, whole groups of
specimens (excepting the very young ones,) have had the outer lamina
of the parietes entirely corroded and removed; in this case the shell
assumes a dirty, more or less dark, ash-colour, feebly tinted with
purple, and the whole surface, owing to the exposure of the solidly
filled-up parietal tubes, becomes finely striated, or covered with
very narrow, longitudinal ridges. When specimens are crowded together
they often become cylindrical, and much elongated, owing to the
basis becoming deeply cup-formed: I have seen specimens, half an
inch in diameter in the widest part, one inch and a half in height,
the walls forming only a third of this. The largest specimen which I
have seen (from the southern shores of England) had a basal diameter
of 1.2 of an inch; some very steeply conical specimens were .9 of an
inch in height, and .8 in basal diameter.

_Scuta_, externally, slightly convex; growth-ridges approximate,
moderately prominent. Internally (Pl. 4, fig. 3 _a_) the articular
ridge is moderately developed, with the lower end produced downwards
into a freely depending, flattened style, somewhat variable in
size, but not so long as in _B. lævis_, and easily broken in
disarticulating the valves. The adductor ridge is very prominent,
running from almost the apex of the valve, close to the articular
ridge, to near the basal margin. The basi-tergal portion of the
valve is converted by the adductor ridge into a rather deep cavity,
within which there is a short, sharp, and minute ridge, close and
parallel to the adductor ridge, and bounding the impression left by
the lateral depressor muscle: this insignificant ridge was present
in every specimen; it occurs only in very few other species, as in
_B. nubilus_ and _cariosus_. The thickness of the valve sometimes
varies a little, and when thick the adductor ridge does not appear
quite so prominent. _Tergum_, with the apex moderately beaked and
produced; beak triangular in section, coloured dark purple, as is
the upper internal surface of the valve; the longitudinal furrow is
deep, and has its edges folded in, and even quite closed. The spur
is moderately long and narrow; but its width varies a little (Pl. 4,
fig. 3 _b_, 3 _c_), and consequently it stands at either rather above
or at twice its own breadth from the basi-scutal angle: its lower
end is either bluntly pointed or square, and generally is feebly
toothed on the under-side. The basal margin of the valve generally
slopes a little, on both sides, towards the spur. Internally, the
scutal margin is but slightly inflected: the articular ridge is but
slightly prominent, and but little curved; in the upper part of the
valve there are generally several very minute ridges, parallel to the
articular ridge, on the side towards the scutum. The internal surface
of the spur itself is sometimes concave. The crests for the carinal
depressor muscle are barely developed. It may here be mentioned that
on the opercular membrane many long spines stand rudely arranged in
rows.

_Parietes_: the parietal tubes have not transverse septa; but
are solidly filled up in their upper parts by dark-purple layers
of shell. The _radii_, as already stated, are either not at all
developed, or are extremely or only moderately narrow, with their
summits more or less oblique: in Mr. Cuming's collection, however,
there is an unique specimen, _var. mirabilis_ (Pl. 5, fig. 1
_c_) with the aperture of the shell as wide as the basis, with
bright purple parietes, and white, very broad radii, having their
summits parallel to the basis. The septa of the radii are finely
denticulated, and the interspaces are filled up solidly. The _alæ_
have very oblique summits, and their edges are finely crenated.
_Basis_, flat, or deeply cup-shaped; there is often an underlying,
coarsely-cancellated layer.

_Mouth_: labrum finely hairy, but without any teeth; mandibles, with
the 4th tooth small; the 5th confluent, with the sometimes smooth,
sometimes pectinated inferior angle. Maxillæ, rather broad, with a
slight notch under the upper pair of spines. _Cirri_, first pair,
with one ramus, having 29 segments, and above one third longer than
the shorter ramus, having 17 segments; these latter segments are
remarkable by the extent to which their upper front surfaces are
laterally produced into projections, twice as long as the breadth of
that portion of the segment which is articulated to the adjoining
segment. These projections have a double row of serrated spines on
their upper edge, and a beautiful radiating bundle at the end; the
projections decrease in length, both in the upper and lower segments.
The second cirrus (Pl. 29, fig. 4) has the segments (13 in number, in
the same individual with the segments above enumerated) of both rami
produced in the same singular manner as in the first pair. The third
pair have only inverted conical segments, coloured darker purple than
the other cirri. The sixth pair had in the same individual 31 or 32
segments, and therefore one or two more than in the longer ramus of
the first pair.[93] The segments in the posterior cirri have their
anterior faces shield-shaped, and bear 6 or 7 pairs of spines, with
some minute intermediate spines. There is the usual point at the
dorsal basis of the penis.

[93] Under the Genus (p. 190) I have given the numbers of the
segments in the cirri of this species at successive ages.

_Range._--This species is common on the southern shores of England
and in the Channel Islands: the largest specimens which I have seen
came from these quarters. The most northern point whence I have
seen specimens, is Tenby, in South Wales. This species is common
throughout the Mediterranean; I have seen specimens from Malaga,
Sicily, Algiers, and Smyrna; thence it ranges down the western
coast of Africa, as far south as the Gambia and Loanda, in 9° south
latitude. I believe British specimens are more often corroded than
those from further south. Amongst some old, ill-kept specimens in a
box in the British Museum, marked "Kingston, Jamaica," there were
some of this species: also I received some specimens, marked "S.
America," from Mr. G. B. Sowerby: again, Ellis, in Phil. Trans., vol.
50, part 11, gives a figure (Tab. 34, fig. 15) of some specimens from
the West Indies, which I believe to be _B. perforatus_: hence, it is
in some degree probable that this species, like _B. tintinnabulum_,
and _amphitrite_, and _improvisus_, may be found on both sides of the
equatorial Atlantic. _Balanus perforatus_ is attached, together with
_B. tulipiformis_, _trigonus_, _amphitrite_, _Chthamalus stellatus_,
and _Pollicipes cornucopia_, usually to rocks, near the lower limit
of the tidal level; but I believe, from specimens kindly sent me
by Mr. Mac Andrew, that it is frequently obtained by dredging;
one specimen was even marked 30 fathoms. According to Poli, it is
sometimes attached to the bottoms of vessels; and I have seen a
specimen adhering to the floating _Lepas Hillii_.

_Affinities._--This is a distinct species, closely allied to no other
species, but comes nearest to _B. lævis_, which is its representative
in Southern America, and on the whole west coast of that continent.
It is allied to that species, and differs from most other species,
in the general form of the shell, its small orifice, narrow radii,
and often deeply cup-formed basis. It agrees to a certain extent in
the colouring, though the purple here is much more prevalent, and
is not confined to the shelly matter filling up the parietal tubes.
It agrees with that species in the general structure of the scutum;
but the two or three deep, longitudinal furrows are here absent; and
the minute ridge, parallel to and almost under the adductor ridge,
is a peculiarity confined to this and very few species in the genus.
The terga differ from those of _B. lævis_, chiefly in the spur
being narrower, and in the apex being beaked. Lastly, the highly
protuberant segments of the one ramus in the first cirrus, and of
both rami in the second pair, are here remarkable. With regard to the
varieties, I have nothing to add to their short diagnostic characters
above given.

18. BALANUS CONCAVUS. Pl. 4, fig. 4 _a_-4 _e_.

BALANUS CONCAVUS. _Bronn._ Italiens Tertiär-Gebilde (1831) et Lethæa
Geognostica, b. ii, s. 1155 (1838), Tab. 36, fig. 12.[94]

---- CYLINDRACEUS, _var._ c. _Lamarck._ Animaux sans Vertèbres
(1818).

LEPAS TINTINNABULUM. _Brocchi._ Conchologia Sub-Appen., t. ii, p. 597
(1814).

[94] I suspect that _B. pustularis_, _miser_, and _zonarius_, all
figured by Münster, in his 'Beiträge,' b. iii, Tab. 6, may be this
species.

_Shell longitudinally striped with white and pink; or dull purple; sometimes wholly white. Scutum finely striated longitudinally; internally, adductor ridge very or moderately prominent._

_Hab._--Panama; Peru; S. Pedro in California; Philippine Archipelago;
Australia. Mus. Brit., Cuming, Stutchbury, Aug. Gould.

_Fossil_ in Coralline Crag, England; Mus. Brit., S. Wood, Bowerbank,
Lyell, J. de C. Sowerby, Tennant. Sub-Appennine formations, near
Turin, Asti, Colle in Tuscany, Mus. Greenough, &c. Tertiary beds,
near Lisbon, Mus. D. Sharpe and Smith. Bordeaux (?) Mus. Lyell.
Tertiary beds, Williamsburg; and Evergreen, Virginia, Mus. Lyell.
Maryland, Mus. Krantz. Recent formations[95] near Callao, Peru, Mus.
Darwin. Red Crag (Sutton) Mus. S. Wood.

[95] I procured this specimen from the Island of S. Lorenzo, off
Callao; it was imbedded, together with seventeen species of recent
shells and with human remains, at the height of eighty-five feet.

This species has caused me much trouble. Looking first to the recent specimens, I examined several from Panama and California, which, though differing greatly in colour, resembled each other in their scuta having the adductor ridge extremely prominent, and in having (Pl. 4, fig. 4 _a_), an almost tubular cavity for the attachment of the lateral depressor muscle,--characters which at first appeared of high specific value; but I soon found other specimens from Panama in which these peculiarities were barely developed. I then examined a single specimen from the Philippine Archipelago, resembling in external appearance one of the Panama varieties, but differing in the scuta being externally strongly denticulated in lines instead of being merely striated,--in the adductor ridge being far less prominent,--and in the spur of the tergum being broader and more truncated; I therefore considered this as a distinct species. I then examined a single white rugged specimen from the coast of Peru, which differed from the Philippine specimen in the shape of the well-defined denticulations on the scuta, and in some other trifling respects, and in the segments of the posterior cirri bearing a greater number of spines; with considerable doubt, I also named this as distinct. But when I came to examine a large series of fossil specimens from the Coralline Crag of England, from northern Italy, from Portugal, and from the southern United States, I at once discovered that the form of the denticuli on the scuta was a quite worthless character,--that in young specimens the scuta were only striated,--that the prominence of the adductor scutorum ridge and the depth of the cavity for the lateral depressor muscle varied much (as in the case of the recent specimens), owing apparently to the varying thickness of the valve,--that in the terga the spur varied considerably in length and breadth, the latter character being in part determined by the varying extent to which the edges of the longitudinal furrow are folded in,--and lastly, that in young specimens the basal end of the spur is much more abruptly truncated than in the old. Hence I have been compelled to throw all these forms, originally considered by me as specifically distinct, into one species. I must repeat that this considerable variation in the prominence of the adductor ridge, and in the depth of the pit for the lateral depressor muscle--the pit in some cases becoming even tubular--is a very unusual circumstance.

With respect to the fossil specimens[96] from the above-stated several distant localities, I consider them as certainly belonging to one species, though varying considerably in several points of structure. When compared with the recent specimens, they differ from them in often attaining a considerably larger size; in the parietes being often, but not always, longitudinally ribbed; and in the radii often having more oblique summits. On the other hand, considering the many points of identity between the fossil and the recent specimen, I have concluded, without much doubt, that they ought all to be classed together. I may remark that, in the Coralline Crag specimens, the spur of the tergum (Pl. 4, fig. 4 _d_), is unusually long and narrow; it is broader and shorter in the Italian specimens (4 _e_), and variable in this respect, in the United States specimens; the scuta of the Lisbon specimens are remarkable for the greater prominence of the adductor ridge, and for the depth of the lateral depressor cavity. Some of the specimens from all the several localities are identical with the recent ones from the coast of Peru. The walls of the shell in the Coralline Crag specimens, are generally ribbed longitudinally. I have entered into the above particulars, on account of, in the first place, its offering an excellent example how hopeless it is in most cases to make out the species of this difficult genus without a large series of specimens; secondly, as showing how the characters alter with age; and thirdly, as a good instance of the amount of variation which seems especially to occur in most of the species which have very extensive ranges.

[96] These will be fully illustrated in the monograph on the Fossil
Balanidæ, to be published by the Palæontographical Society.

Some of the pink-striped Panama varieties, though having a somewhat different aspect, can be distinguished from certain varieties of _B. amphitrite_ only by their scuta being longitudinally striated,--a character in this species variable in degree, and in most cases of very little value. Some of the other recent varieties are sufficiently distinct from _B. amphitrite_; and the great fossil Coralline Crag specimens, which stand at the opposite end of the series of varieties, with their ribbed walls, very oblique radii, and coarsely striated scuta, are extremely unlike _B. amphitrite_. With respect to the nomenclature of the present species, I have little doubt that I have properly identified the Italian fossil specimens with _B. concavus_ of Bronn, who has given a very good figure of this species in his 'Lethæa Geognostica;' it must, however, be confessed that the longitudinal striæ on the scuta are not there represented. Considering the large size and frequency of this species in Europe and in the United States, it has probably received several other names, besides the two incorrect synonyms, quoted at the head of this description. I should add that the true _B. cylindraceus_ (not _var._ C) of Lamarck, according to the plate given by Chenu in his 'Illust. Conch.,' is the _B. psittacus_ of South America. I have seen in collections specimens of _B. concavus_ labelled as _B. tulipa_ of Poli (_B. tulipiformis_ of this work),--a very natural mistake, without the opercular valves be carefully examined.

_General Appearance._--Shell conical, often steeply conical; orifice
rather small, with the radii narrow, and generally in the fossil
specimens very oblique; surface generally smooth, sometimes rugged,
and in the coralline crag specimens generally ribbed longitudinally,
the ribs being narrow. Colour various, either dull reddish-purple
with narrow nearly white, or wider dark longitudinal bands; or,
again, pale rosy-pink with broad white bands; or lastly, wholly
white. The radii are either darker or paler than the parietes. The
opercular valves are either dark purple or nearly white. Pale pink
and white stripes are visible on some of the Italian and Portuguese
tertiary specimens; and in most of the fossils the sheath is tinged
dull red.

_Dimensions._--The largest actually recent specimen which I have
seen, from the Philippine Archipelago, had a basal diameter of 1.2
of an inch; the Peruvian pleistocene specimen is 1.7 in diameter;
specimens from the crag and from the Italian deposits, however,
sometimes slightly exceed two inches in basal diameter, and three in
height.

_Scuta_: these in young and moderately-sized specimens are striated,
sometimes very faintly, but generally plainly, causing the lines of
growth to be beaded; but often, in large and half-grown specimens,
the lines of growth are extremely prominent, and being intersected by
the radiating striæ, are converted into little teeth. As the striæ
often run in pairs, the little teeth frequently stand in pairs,
or broader teeth have a little notch on their summits, bearing
a minute tuft of spines. In very old and large specimens, the
prominent lines of growth are generally simply intersected by deep
and narrow radiating striæ. In one case, a single zone of growth in
one valve was quite smooth, whilst the zones above and below were
denticulated. The valve varies in thickness, which I think influences
the prominence of the lines of growth and the depth of the striæ.
These striæ often affect the internal surface of the basal margin,
making it bluntly toothed. The articular ridge is rather small,
and moderately reflexed: the adductor ridge (as already stated,)
varies remarkably; in most of the Panama specimens, it is extremely
prominent, and extends down to near the basal margin; in other
specimens it is but slightly prominent, especially in some of the
fossil specimens from Virginia. The cavity for the lateral depressor,
also, varies greatly; it is often bounded on the side towards the
occludent margin by a very slight straight ridge, which occasionally
folds a little over, making almost a tube; this, at first, I thought
an excellent specific character, but far from this being the case,
the cavity often becomes wide, quite open, and shallow.

_Terga_, very slightly beaked; the surface towards the carinal end of
the valve, in some of the fossil specimens, is very slightly striated
longitudinally. There is either a slight depression, or more commonly
a deep longitudinal furrow, with the edges folded in and touching
each other, extending down the valve to the spur, and causing the
latter to vary in width relatively to its length. When the furrow
is closed in, the spur is about one fourth of the entire width of
the valve, and has its lower end obliquely rounded, and stands at
about its own width from the basi-scutal angle: when there is only
a slight depression and no furrow (as is always the case with young
specimens), the spur is broader, equalling one third of the width
of the valve, with its lower end almost truncated, and standing at
about half its own width from the basi-scutal angle. But the absolute
length of the spur, also, varies considerably; it is often very long,
compared to the whole valve. The basal margin on the carinal side
is sometimes slightly hollowed out; when the furrow is closed, this
latter side slopes towards the spur. Internally, the articular ridge
and crests for the tergal depressor muscle are moderately prominent.

_Parietes_, the longitudinal septa sometimes stand near each
other, making the parietal pores small. The _radii_ have oblique
summits, but to a variable degree; their septa are unusually fine,
and are denticulated on their lower sides; the interspaces are
filled up solidly. The _alæ_ have their summits very oblique,
with their sutural edges nearly or quite smooth. In most of the
fossil specimens, and slightly in some of the recent specimens, the
surface of the sheath presents an unusual character, in a narrow,
longitudinal, slightly raised border, running along the sutures, on
the carinal side of each compartment.

_Basis_ thin, porose; sometimes with an underlaying cancellated layer.

_Mouth_: labrum with six teeth: mandibles with the fourth and fifth
teeth small, either sharp, or blunt: maxillæ with a straight edge,
or with the inferior part slightly prominent. _Cirri_ with the rami
of the first pair unequal by four or five segments: the segments in
the shorter ramus are extremely protuberant. The segments in the
second cirrus only moderately protuberant: but all the specimens were
in bad condition, and it appeared as if, in the Panama specimens,
the segments of the second cirrus were more protuberant than in the
Philippine Island specimens. In the posterior cirri there are from
three to five pairs of spines on each segment: even amongst the
Panama specimens some had three and some four pairs, and a white
Panama specimen had five pairs of spines.

All the recent specimens which I have seen, were, with one exception, attached to various shells and crabs, and to each other. The Peruvian specimen was associated with _B. flosculus_. The tertiary specimens are often congregated together into great masses. Including the recent and fossil specimens, this species encircles the globe. During the miocene period it seems to have been the commonest existing sessile cirripede; now, it does not appear to be common, excepting, perhaps, at Panama: Mr. Cuming procured only one specimen from the Philippine archipelago.

19. BALANUS AMPHITRITE. Pl. 5, fig. 2 _a_-2 _o_.

LEPAS RADIATA. _Wood's_ General Conchology (1815), Pl. 7, fig. 7.

---- MINOR? _Wood's_ General Conchology (1815), Pl. 7, fig. 6.

---- BALANOIDES. _Poli._ Testacea utriusque Siciliæ (1795), Tab. 5.

BALANUS BALANOIDES. _Risso._ Hist. Nat. de l'Europe Merid., tom. iv,
1826.

_Shell longitudinally striped with purple or pink; sometimes with the stripes confluent; sometimes wholly white. Scutum internally with a prominent broad adductor ridge._

_Var._ (1) communis: (2 _e_, 2 _h_, 2 _l_,) _nearly white, with
pale or dark violet-coloured longitudinal stripes: epidermis rarely
persistent: shell either thin or thick: radii white or freckled
with reddish mahogany colour, with their summits either oblique,
sometimes in a high degree, or nearly parallel to the basis: basal
point of spur of the tergum either square or bluntly pointed_. Hab.
Mediterranean, W. Indies, S. Africa, Philippine Archipelago, New
South Wales.

_Var._ (2) venustus: (2 _a_,) _white or pale pink, with narrow bright
pink, or broad pinkish-purple stripes; orifice either much dentated
or nearly entire. Tergum with the carinal half of the basal margin
sometimes much hollowed out_. Hab. W. and S. Africa, Ceylon.

_Var._ (3) pallidus: (2 _c_, 2 _k_,) _white, with or without a
yellowish persistent epidermis; sometimes with the edges of the
compartments tinted purple: radii moderately oblique: tergum
generally narrow, with the spur sharp, and the basal margin on its
carinal side much hollowed out_. Hab. W. Africa, Madagascar, Red Sea.

_Var._ (4) niveus: (2 _f_,) _white, with longitudinal hyaline lines;
epidermis not persistent_. Hab. W. Indies, Florida, S. Africa, &c.

_Var._ (5) modestus: _upper part of shell white, lower part uniform
blueish-gray, opercular valves as in_ Var. (1). Hab. unknown.

_Var._ (6) Stutsburi: (2 _d_, 2 _i_, 2 _m_, 2 _n_, 2 _o_,) _white,
with or without pinkish-purple stripes, which are often confluent,
rendering the lower part of the shell of a uniform purplish tint;
epidermis persistent: radii very narrow: tergum narrow, spur sharp,
varying in form and in exact position; carinal margin sometimes
highly protuberant; basal margin on the carinal side of the spur
generally, but not invariably, much hollowed out_. Hab. West Africa.

_Var._ (7) obscurus: (Pl. 5, fig. 2 _g_,) _with narrow, approximate,
obscure and often almost confluent, slaty, or pale purplish-brown,
or dark slate-coloured stripes_. Hab. West Indies, Australia, and
unknown.

_Var._ (8) variegatus: _with narrow, approximate, dusky,
claret-coloured stripes, transversely freckled with white; shell
conical; walls very thin: scutum with the adductor ridge small_. Hab.
New Zealand.

_Var._ (9) (_an. spec._?) cirratus: (fig. 2 _b_,) _shell very pale
purplish-brown, with faint, more or less plain longitudinal stripes,
transversely freckled with white; walls thin: scuta with the lines of
growth beaded: basis, in specimens growing in groups, irregularly cup
formed: maxillæ with the inferior corner extremely prominent_. Hab.
Mouth of Indus, Australia, Philippine Archipelago.

_Hab._--Warmer temperate and tropical seas; extremely common;
Mediterranean, Smyrna, Sicily, Coast of Portugal; West Coast of
Africa, River Gambia, West Indies, Demerara, Natal, Madagascar, Red
Sea, Mouth of the Indus, Ceylon, Philippine Archipelago, East Indian
Archipelago, Pacific Ocean, east coast of Australia, New Zealand;
extremely common on ships' bottoms; often attached to floating
timber, canes, &c.; often associated with _B. tintinnabulum_;
attached to pebbles and various shells.

With respect to the nomenclature of this extremely common species, which is widely distributed in all the warmer seas (excepting, as far as I have seen, on the west coast of America), there is some difficulty. I have no doubt that it is the _Lepas radiata_ of Wood (1815), but Bruguière, in 1789, gave this same name to a Balanus which he had not seen, but which is figured in Chemnitz, Tab. 59, fig. 842. I should have thought that this also had been the present species, but Spengler, in describing (Skrifter af Naturhist. Selskabet i, B. 1790) this individual specimen, which he calls _L. purpurea_, states that it is 13 lines in basal diameter; now this is a size which is never acquired by _B. amphitrite_; and the description, habits, and size, would apply equally well to the species which I have called _B. amaryllis_; but when no notice is taken of such points of importance, as whether the walls are permeated by pores, whether the radii are smooth-edged, whether the scuta are striated, it is impossible to identify with any approach to certainty sessile Cirripedes; and the names given ought, in my opinion, to carry little weight with them. With respect to Lamarck's _Balanus radiatus_ (1818), the synonyms quoted exhibit some great and inextricable confusion. The _B. radiatus_, again, of Risso, is a fossil and apparently distinct species. There can be no doubt that the present species is the _Lepas balanoides_ of Poli, (and of several authors who have followed him), and equally little doubt that the present species is not the true _L. balanoides_ of Linnæus, which has a membranous basis, and which I have not seen from the Mediterranean. Under these circumstances I have concluded that less confusion would be caused by giving a new name to this species than by taking that of Wood, which ought not to have been used by him, considering Bruguière's previous adoption of it.

Under the head of _B. tintinnabulum_ I have alluded to the great variation of _B. amphitrite_, which consists not only in a vast diversity in the colouring and in the general aspect, but likewise in the degree of obliquity of the summits of the radii, in the form of the terga, and slightly in that of the scuta. In order to show that it has not been from indolence that I have put so many forms together, I may state that I had already named and fully described in detail eight of the following forms as species, when I became finally convinced that they were only varieties: it would require at least thirty figures, which I have not the power to give, fully to illustrate the transitional forms. As with _B. tintinnabulum_, the deception is wonderfully enhanced by whole groups of specimens from the same locality exactly resembling each other, and sometimes differing from other groups attached to the very same object. If a person were to get together only some fifty or sixty specimens from only half a dozen different localities, he would almost certainly come to the same conclusion, as I at first did, that several of the varieties are true species; but when he gets several hundred specimens from all quarters of the globe, he will find, to his trouble and vexation, that character after character fails and blends away by insensible degrees, and he will be led, as the more prudent course, to include, as I have done, and I hope rightly, all under one specific name. I have experienced more doubt regarding the last variety, _cirratus_, than on any other, on account of its peculiar colouring, and from the basis being often irregularly cup-formed. Under _B. concavus_ I have remarked how closely some of its varieties approach to _B. amphitrite_, and it is to this last variety that they approach; almost the only difference being that the scuta in _B. concavus_ are longitudinally striated. Yet some of the varieties of the two species are so distinct that it would be puerile to class them together. I will only add, that after studying such varying forms as _B. tintinnabulum_ and _amphitrite_ it is difficult to avoid, in utter despair, doubting whether there be such a thing as a distinct species, or at least more than half a dozen distinct species, in the whole genus Balanus.

As with _B. tintinnabulum_, I will first give a full description of the more common forms, alluding only to each less frequent variation, and then separately describe briefly the more marked varieties.

_General Appearance._--Shape conical, either steep or considerably
depressed; sometimes tubular; orifice either nearly entire or deeply
toothed, not large, varying from rhomboidal to rounded-trigonal.
Surface of shell smooth, never ribbed, generally naked, but
occasionally the yellowish epidermis is persistent; in the same
individual, I have seen all the lower part of the shell thus covered
and the upper part naked, the line of separation being defined.
The _colour_ varies much, even sometimes considerably on the same
individual; generally white or pale gray, with dull violet-coloured,
longitudinal, moderately broad stripes; these stripes are sometimes
equidistant, but more usually they are arranged so as to leave
broad white spaces; the stripes fade away by endless variations,
the edges of the compartments and the carinal end of the shell
longest retaining any colour, until we have a uniformly white
shell, generally covered with a yellowish epidermis; or the white
is longitudinally marked with hyaline lines; this latter variety
has a very peculiar aspect, and I did not doubt it was specifically
distinct, until, in a number of specimens on a ship from the West
Indies, I got the most perfect series, and another scarcely less
perfect series from the Mediterranean, graduating into common
coloured varieties. Rarely the dull violet or purple stripes become
approximate and dark, so that the whole shell is tinted of a brownish
slate-colour, occasionally freckled with white. Again, we have
another set of very pretty varieties, with a white or very pale
pink ground, with either narrow bright pink or broad pinkish-purple
stripes. Again, I have seen numerous specimens of a variety, _var.
Stutsburi_, from the west coast of Africa, in which the upper part
of the shell is white, and the lower part shaded with pinkish or
dark purple approximate stripes, which often become confluent; in
one group, the whole shell being thus uniformly coloured, without
any vestige of stripes. I have seen another group from an unknown
locality, in which the lower part of the shell was uniformly
blueish-gray. A variety from Australia has narrow approximate dark
claret-coloured stripes, transversely freckled with white. Lastly, in
the variety _cirratus_, the whole shell is very pale purplish-brown,
with indistinct longitudinal brownish stripes, transversely freckled
with white lines. I considered this as a distinct species, until
quite lately finding forms which I could not possibly determine
whether to class as _B. cirratus_ or _amphitrite_.

The radii are generally snow-white, or freckled with a bright
mahogany tint, or rarely clouded with purple, or in the pink
varieties with pink. The scuta are dull purple or pink, generally
with a white band along their tergal margin; often, however, they
are white, with merely one or two purple fasciæ. The thickness or
strength of the shells varies much; some specimens attached to a
floating cane, from Natal and the Philippine Archipelago, were
extremely strong; others, from the Mediterranean and Australia,
and some tubular varieties from the West Indies, were very thin,
translucent, and fragile. _Size_: large specimens generally attain a
diameter of from half to three quarters of an inch in basal diameter;
and I have seen one or two specimens an inch in diameter.

_Scutum_; sometimes the surface is very smooth, but generally the
growth-ridges are moderately prominent; the latter are occasionally
very finely beaded, and this seems always the case with _var.
cirratus_. Internally, the articular ridge is prominent and reflexed:
the adductor ridge is sharp, very prominent, and straight; it runs
parallel to the occludent margin; close to its lower side there is
often a depression (Pl. 5, fig. 2 _i_), sometimes bounded by a slight
ridge, as if for the attachment of a muscle, but there certainly is
no muscle here: rarely the adductor ridge is only slightly prominent:
there is a small and shallow little pit of variable depth for the
lateral depressor muscle.