B. CRENATUS. _Bruguière._ Encyclop. Method. (des Vers) 1789.
LEPAS FOLIACEA, _var. a_. _Spengler._ Skrifter af Naturhist.
Selskabet, b. i, 1790.
---- BOREALIS. _Donovan._ British Shells, Pl. 160 (1802-1804).
B. RUGOSUS. _Pulteney_ (?) Catalogue of Shells of Dorsetshire,
1799.
---- ---- _Montagu_ (?) Test. Brit. 1803.
---- ---- _Gould_ (!). Report on Invertebrata of Massachussetts
(1841), fig. 10.
B. GLACIALIS (?) _J. E. Gray._ Suppl. Parry's Voyage, 1819.
B. ELONGATUS (!), CLAVATUS (!), _Auctorum variorum_.
_Shell white: radii with their oblique summits rough and straight.
Scutum without an adductor ridge: tergum with the spur rounded._
_Hab._--Great Britain, Scandinavia, Arctic Regions as far as
Lancaster Sound, in 74° 48′ N. (Mr Sutherland); Behring's Straits
(Captain Kellett); United States; Mediterranean; West Indies, (Mus.
Brit.); Cape of Good Hope, (Mus. Krauss). Generally attached to
shells and crustacea in deep water; sometimes to ships' bottoms. Very
common.
_Fossil_ in glacial deposits of Scandinavia and Canada, Mus. Lyell;
in the mammaliferous, and Red, and Coralline Crags, Mus. S. Wood, J.
de C. Sowerby, Bowerbank; Miocene formation, Germany, Mus. Krantz.
I find, in most collections, this species confounded with _B.
balanoides_; I have even seen the two species, placed by Leach, on
the same tablet in the British Museum: _B. balanoides_ is, moreover,
generally confounded with _Chthamalus stellatus_; nor has any one
hitherto separated the present species from _B. improvisus_. On the
other hand, trifling varieties, both of _B. balanoides_ and _B.
crenatus_, have commonly been considered as specifically distinct. From
these facts it will be seen in what confusion our commonest British
species of Balanus have been left. After due deliberation, I have
little doubt that this is the _B. crenatus_ of Bruguière, and probably
the _B. rugosus_ of Montagu, but this latter author omits all reference
to the really important diagnostic characters between this species and
_B. balanoides_. The _B. crenatus_ is certainly the _B. rugosus_ of Dr.
Aug. Gould. In various collections, I find specimens of _B. crenatus_,
when coming from the arctic regions, called _B. glacialis_, _arcticus_,
and _borealis_; though I have not met with an authentic specimen of the
_B. glacialis_ of Gray ('Supp. Parry's Voyage,' 1819, p. ccxlvi), I
have little doubt that it would prove to be the present species.
_General Appearance._--White, usually of a dirty tint, from the
yellowish or brownish persistent epidermis: conical, generally
(fig. 6 _a_) with the parietes rugged and irregularly folded
longitudinally; but sometimes much depressed and extremely smooth (6
_b_); often cylindrical and very rugged; occasionally club-shaped (6
_c_), the upper part being much wider than the lower: specimens in
this latter condition sometimes have extremely narrow parietes, like
mere ribs, and wide radii. The orifice in the cylindrical varieties
is often most deeply toothed. The radii are generally narrow, and
have jagged oblique summits; but not infrequently they are so narrow
as to form mere linear borders to the compartments. The orifice is
rhomboidal, passing into oval, either very deeply or very slightly
toothed.
_Dimensions._--The largest British specimen which I have seen was
only .55 of an inch in basal diameter: specimens from Greenland
and the northern United States frequently attain a diameter of
three-quarters of an inch, and I have seen one single somewhat
distorted specimen actually 1.6 of an inch in basal diameter. The
specimens from the glacial deposits of Uddevalla and Canada appear,
on an average, to attain as large or larger dimensions than those
from the United States: on the other hand, the specimens from the
mammaliferous and Red Crag are smaller, the largest being only .35 in
basal diameter. When individuals have grown crowded together, their
length is often twice, and even occasionally thrice, as great as
their greatest diameter; thus I have seen a Greenland specimen 1.6 of
an inch in length, and only .75 in diameter. In the British Museum
there are some arctic specimens, one and a half inch in length, only
half an inch in diameter at the summit (fig. 6 _c_), thence tapering
downwards to a blunt point.
_Scuta_; the lines of growth are but little prominent: the surface
is generally covered by disintegrating membrane. The upper ends
are usually a little reflexed, so that the tips project freely as
small flattened points. Internally, the articular ridge is highly
prominent and somewhat reflexed: there is no adductor ridge, but a
very distinct impression for the adductor muscle: the depression for
the lateral depressor muscle is small, but variable. The _terga_
are rather small: the spur is short, and placed at rather less than
its own width from the basi-scutal angle; the basal margin slopes a
little towards the spur, of which the lower end is rounded or bluntly
pointed in a variable degree. There is no longitudinal furrow, hardly
even a depression. Internally, the articular ridge is very prominent
in the upper part; the crests for the tergal depressores are well
developed, but variable.
_Compartments._--The internal carinal margin of each compartment,
from the sheath to the basis, generally, but not invariably, projects
a little inwards beyond the general internal surface of the shell,
in a manner not common with the other species of the genus: the
basal edge of this projecting margin rests on the calcareous basis,
and is crenated like the basal edges of the longitudinal parietal
septa. The whole internal surface of the shell is ribbed, but the
ribs are not very prominent. The parietal tubes are large, and are
crossed in the upper part, and often low down, by transverse thin
septa: the longitudinal parietal septa are only slightly denticulated
at their bases; occasionally they divide at the basis close to the
outer lamina of the parietes, making some short outer subordinate
pores. In the circular furrow beneath the lower edge of the sheath,
there are sometimes little ridges, dividing it into small cells:
sometimes, however, this furrow is filled up by irregular knobs of
calcareous matter. The _radii_ are always rather narrow, and often
they form mere linear ribbons of nearly uniform width along the
edges of the compartments. Their summits or edges are always more or
less irregular and jagged: they form an angle with the horizon of
generally above 40°. Their septa are fine, and barely or not at all
denticulated. The alæ have oblique summits: their sutural edges are
rather thick and distinctly crenated. _Basis_ flat, calcareous, very
thin, with the surface slightly marked by radiating furrows, which
furrows answer to the radiating pores that occur in the bases of most
species. In a club-shaped arctic specimen, one inch and a half in
length, the summit being half an inch and the base only one fifth of
an inch in diameter, the basis was still calcareous, thick, and not
permeated by pores.
_Mouth_: labrum with six teeth: mandibles with the fourth tooth
minute or rudimentary, and the fifth generally confluent with the
inferior angle. Maxillæ with generally, but not invariably, a small
notch under the upper pair of great spines. _Cirri_, first pair with
the rami very unequal in length, one ramus being nearly twice the
length of the other; in a large specimen having a cylindrical shell
the proportional numbers of the segments in the two rami of the first
cirrus were ten to twenty-three; in a small conical specimen the
numbers were only eight to thirteen. The second cirrus has only two
or three more segments than the shorter ramus of the first pair: the
third cirrus has one or two more segments than the second; but it is
nevertheless decidedly longer than the second. On the dorsal surfaces
of both segments of the pedicel of the third cirrus, there is a
tuft of fine spines. The segments of these three pairs of cirri are
not much protuberant in front. The segments of the posterior cirri
have, each, four, or five, or six pairs of spines. _Penis_, with a
straight, sharp, short point on the dorsal basis.
_Range, habits, &c._--I have received specimens from all parts of the
coast of Great Britain and Ireland, generally attached to crustacea
and mollusca, and never hitherto from rocks uncovered by the tide.
This species is also attached to floating timber, sticks, fuci, and
occasionally to pebbles at the bottom of the sea. Mr. Thompson has
sent me specimens from twenty-five fathoms depth in Belfast Bay:
others on a Pinna from _about_ fifty fathoms on the coast of Antrim;
others from between three and six fathoms attached to Laminaria
digitata: there is a specimen in Mr. Jeffreys' collection marked
forty-five fathoms. It is often associated, both on the coasts of
America and Britain, with _B. porcatus_, and though these species are
so distinct, yet when both have their surfaces similarly affected by
being attached, as is often the case, to large Pectens, it is not at
first easy, by external characters, to distinguish them, except by
close inspection of the terga, which in _B. porcatus_ are beaked and
purple. The _B. crenatus_ is sometimes associated in deep water with
_B. Hameri_. At Ramsgate, in Kent, I saw a rudder of a ship, in which
the two or three upper feet were thickly coated with _B. balanoides_,
and the two or three lower feet with _B. crenatus_ and _improvisus_
mingled, together with a few of _B. balanoides_: occasionally
vessels are thickly encrusted with this species, but I have never
seen an instance of its concurrence with _B. tintinnabulum_ and
_amphitrite_--the commonest species on ships coming from the south.
I have seen specimens from Greenland, Baffin's Bay, the coast of
Labrador, and other specimens marked simply, "Arctic regions," and,
again, others from the shores of Maine and Massachussetts. The arctic
specimens, and those from the northern United States, are larger
than the British. I have seen one single minute specimen on a crab,
marked as having come from the Mediterranean. In the British Museum,
amongst some specimens of _B. eburneus_, ticketed as having been sent
from Jamaica, there was a small group of specimens, differing in no
one essential respect from the common varieties of _B. crenatus_:
at first I concluded that this was an erroneous habitat, and that
the specimens had really come from the United States, where _B.
eburneus_, is found as well as in the West Indies: for it appeared
to me exceedingly improbable that an animal which can exist in lat.
75° N. should inhabit the hot shores of Jamaica: but subsequently I
have received a specimen from Prof. Krauss, collected by himself in
Algoa Bay, which is perfectly characterised, and even has the little
cells in the furrow under the sheath: so that I am compelled to admit
this enormous range and capability of resisting the most extreme
climates. That this species should live in the tropical seas is the
more surprising, as the large size of the specimens in the northern
seas and in the glacial deposits, might fairly have been supposed
to have indicated special adaptation for a cold climate. The great
geographical range of this species accords with its range in time
from the present day to the Coralline Crag period.
The specimens from the glacial deposits which I have examined,
chiefly in Sir C. Lyell's collection, are very fine and large; they
are often associated, like the now living individuals, with _B.
porcatus_ and _Hameri_: they come from the well-known formation of
Uddevalla and from Canada. There are well-characterised specimens
in the mammaliferous Crag, at Bramerton and near Norwich, in Sir C.
Lyell's collection, and from Sutton and other places in the Red Crag
of the eastern shores of England: these specimens are decidedly not
only smaller than the glacial, but than the recent English specimens;
for the largest Crag specimens which I have seen had a basal diameter
of only .35 of an inch. The specimens which I have seen from the
Coralline Crag, and some others sent me by Krantz from the miocene
formation of Flonheim bei Abzei, in Germany, had not their opercular
valves, yet I cannot doubt, considering how few species there are in
the present section of the genus, that I have rightly identified them.
_Diagnosis._--Under the head of _B. balanoides_ I shall make a few
remarks on the diagnosis between that and the present species; as _B.
improvisus_ is found on the British shores, sometimes mingled with
_B. crenatus_, I may observe that, externally, the only difference
consists in the edges of the radii in _B. improvisus_ being much
smoother and rounded, and in the whole shell being less rugged.
Internally, in _B. improvisus_ the porose basis, the presence of an
adductor ridge on the under side of the scutum, the graduated teeth
on each side of the central notch in the labrum, and the little
inequality in length of the rami of the first pair of cirri, are
clearly and amply diagnostic.