LEPAS PSITTACUS. _Molina._ Hist. Nat. Chile (1788), vol. i, p. 223.
BALANUS PICOS. _Lesson._ Zoolog. Voyage de la Coquille (1829).
---- TINTINNABULUM (var. c). _Ranzani._ Mem. di Storia Nat. tab. 3,
fig. 1-3 (1820).
---- CYLINDRACEUS. _Lamarck_, in _Chenu_. Illust. Conch. Tab. 4,
fig. 17, Tab. 5, fig. 7, sed non var. (_c._) in Lamarck,
Animaux sans Vert., (1818).
---- PSITTACUS. _King_ and _Broderip_. Zoolog. Journal, vol. v
(1832-1834), p. 332.
_Shell, pale dirty pink; orifice hexagonal. Scutum with the articular
ridge very small, confluent with the very prominent adductor ridge,
forming a tubular cavity, which extends up to the apex of the valve.
Tergum with the apex produced, needle-like, purple: spur placed at less
than its own width from the basi-scutal angle._
_Hab._--Peru, Chile, Chiloe, Patagonia. Fossil in an ancient tertiary
deposit, Coquimbo; and in a superficial, recent bed at S. Josef, in
Patagonia.
_General appearance._--Shell either almost cylindrical or steeply
conical, generally flesh-coloured, sometimes pale pink; surface
either smooth (when not disintegrated) or sometimes with the parietes
distinctly and rather strongly ribbed, with the ribs distant from
each other: I have seen six or seven ribs on the rostrum alone. The
orifice in the most perfect specimens is nearly equilateral and
hexagonal. The radii generally are very broad, but occasionally
quite narrow, and even linear. The basis is generally deeply and
irregularly cup-formed.
_Size._--This is the largest species in the family: I have seen a
specimen six inches in length and three and a half in diameter; and
another specimen no less than nine in length, though only two and a
half inches in diameter.
_Scuta._--In full-sized specimens the surface is finely striated
longitudinally, caused by the lines of growth being minutely sinuous;
but in young specimens, until they attain a basal diameter of above
half an inch, the surface is smooth. The valve is transversely
arched, a line of flexure running from the apex to the basal margin,
at about one third of the width of the valve from the tergal margin.
The basal margin is curved nearly continuously, and extends nearly
half-way up the valve; hence the basi-tergal corner is largely
rounded off. The articular ridge is but little prominent, and is not
reflexed: the articular furrow is very narrow. The adductor ridge
consists of a sharp, much-projecting plate, running down close to the
basal margin, and is confluent with the lower part of the articular
ridge. This plate and the inflected tergal margin of the valve,
together form a large and deep cavity, which extends up almost to the
apex of the valve. The depressor muscle is attached in the middle, at
the lower, open end of this cavity.
_Terga._--These are strongly beaked, the beak being from one third
to one fourth of the total length of the valve, including the spur:
the beak is very sharp, somewhat flattened, and bowed; when young,
and when well preserved, it is coloured purple: it is penetrated
by a fine tubular cavity, occupied by a thread of corium, which
extends about half-way up it. The whole valve is narrow, being about
thrice as long as wide. The spur is also long and narrow; it is
seated at less than its own width from the basi-scutal angle. The
scutal margin is not much inflected. The longitudinal furrow has its
sides, in full-grown specimens, closely folded together. The basal
margin slopes down on both sides to the spur. There are no crests,
or only traces of them, for the attachment of the depressor muscle.
Internally, the spur is prolonged, as a prominent ridge, upwards to
the beak, and serves as an articular ridge. In the middle, in the
upper part (Pl. 2, fig. 3 _d_), between this articular ridge and the
carinal margin, there is a second narrow ridge, which extends from
the lower part of the beak half-way down the valve, and then dies
out. The space between these two ridges, and the ridges themselves,
are coloured purple, and consist of harder shell than the rest of
the valve; hence, when the outer surface and the adjoining scutal and
carinal margins disintegrate, this part remains, and so forms the
beaked, purple apex.
_Compartments._--The parietal tubes are unusually large in proportion
to the size of the shell, and run up to the summit without any
transverse septa: the longitudinal septa are strongly denticulated.
The radii are penetrated by large tubes; their septa are very
strongly denticulated, and the denticuli themselves often subdivide
and branch out at their extremities. The sutural edges of the alæ
are smooth, or with a high power can just be seen to be crenated.
The radii are generally very highly developed, so that their summits
are even wider than the bases of the parietes; but, on the other
hand, in some few large specimens, the radii are either very narrow
or absolutely linear. In these latter cases, the diametric growth
has nearly or altogether ceased, whilst the walls of the shell have
continued to be added to at their bases, their summits at the same
time suffering disintegration; and thus the orifice has increased in
size.
_Basis_ generally, and occasionally very deeply, cup-formed. An
unusually thick cancellated layer in most cases forms the under side
of the basis.
_Mouth._--Labrum apparently without teeth, or with very minute ones:
mandibles with three teeth, of which the third is thicker than the
first or upper one: the fourth and fifth teeth are confluent with the
inferior angle. The maxillæ have a small notch under the upper pair
of spines; inferior part projecting and supporting two spines, placed
one below the other, and equalling in size the upper pair. _Cirri_:
the rami of the first cirrus are unequal by four or five segments;
shorter ramus and both rami of the second cirrus with the segments
extremely protuberant: posterior cirri not much elongated, with the
segments rather broad, supporting six pairs of spines.
_General Remarks._--This, which is much the largest known species
of the genus, ranges from Peru (Arica being the most northern spot,
whence I have seen specimens), along the coast of Chile, where it
is very abundant at a few fathoms' depth, at least as far south as
Southern Chiloe; it is said by Captain King to attain the largest
size at Conception. On the coast of Eastern Patagonia, I dredged
up this species from nineteen fathoms, in lat. 49°. In lat. 42°
(S. Josef), on the same eastern coast, I found fossil specimens
in beds of sand upraised between eighty and one hundred feet. In
the tertiary formation at Coquimbo, in Chile, it occurs in the
middle bed, associated with the recent _B. lævis_, and with various
mollusca, all of which are apparently extinct, indicating that the
formation is of considerable antiquity. In the living state, on
the coast of Chile, it is often associated with _B. lævis_. As it
frequently adheres to large specimens of the Concholepas, it must
sometimes be an inhabitant of shallow water. I have seen one specimen
attached to _Mytilus Magellanicus_. Mr. Cuming believes that about
six fathoms is the usual depth at which it lives. Numerous specimens
are often congregated together into great masses. Mr. Stutchbury has
some interesting specimens which he procured from a ship that had
first sailed to Ichaboe, on the coast of Africa, and afterwards
to Patagonia; consequently numerous specimens of _B. psittacus_
had become attached on _B. tintinnabulum_, and subsequently during
the voyage home, some few of the latter again had adhered on _B.
psittacus_: the contrast in the paler colour and hexagonal orifice
of this species, with the darker tints and more trigonal orifice of
_B. tintinnabulum_ was striking. At Coquimbo, in Chile, I procured
a specimen of _B. psittacus_, attached to a chain cable which had
been in the water only six months; this specimen measured 1.3 of an
inch in basal diameter, and .8 in height: this shows a rapid rate of
growth. Lastly, I may mention that it is asserted by Molina, and I am
assured by Mr. Cuming that the statement is perfectly correct, that
this Balanus, when cooked, is universally esteemed as a delicious
article of food.