XENOBALANUS. _Steenstrup._ Videnskabelige Meddelelser. Aaret, 1851.
SIPHONICELLA (sine descript.) _Darwin._ Monograph on the Lepadidæ, p.
156 (1852).
_Shell almost rudimentary, star-formed, composed of six compartments,
with a long peduncle-formed body rising from the middle: opercular
valves none._
_Hab._--North Atlantic Ocean, attached to Porpoises; Mus. R. T. Lowe,
Steenstrup.
This Cirripede, in appearance the most anomalous of its family, has
affinities distinctly pronounced. Four years ago the Rev. R. T.
Lowe sent me some specimens, which he had obtained from a porpoise
between Madeira and England; and I named them in MS. Siphonicella,
from their relationship to Tubicinella,--a fact which I mention only
because Sir C. Lyell has alluded to this genus under the above name
(without any description), in his anniversary address to the Geological
Society, as have I, in my volume (p. 156) on the Lepadidæ. Since that
time Professor Steenstrup has described and named the genus, fully
recognising its place and affinities, and has most kindly sent me a
magnificent group of specimens.
This genus singularly resembles, in general appearance, some of
the pedunculated Cirripedes, so much so that in the specimens sent
me by Mr. Lowe, in which the almost rudimentary shell was, from
disintegration and its deep imbedment, not plainly visible, I did not
in the least doubt that I was examining a new genus of Lepadidæ. I may
mention, as a proof how truly all the parts and organs are correlated
in Cirripedes, that I was at first in despair when I found a species
to all appearance pedunculated, with its labrum not bullate, its palpi
of large size, its third pair of cirri totally unlike the fourth and
succeeding pairs, and with only a single layer of muscles round the
peduncle; but when, in addition, I found that there were branchiæ,
and that these were double, I felt convinced that I was dissecting a
disguised sessile cirripede, and that its true place was near Coronula:
soon, I found the imbedded and almost rudimentary shell, of which a
mere fragment would equally well have declared the true position and
relationship of the whole animal. Though Xenobalanus, in external
aspect, is so completely masked, yet in its habits, namely, in living
attached on Cetaceans, as in its essential structure, it displays its
real affinities. In the course of the following description, it will
be seen that in the shell, the affinity is almost equally close to
Coronula and Platylepas, but that, considering the whole animal, the
affinity is somewhat closer to Tubicinella. Xenobalanus may indeed
be described as a Tubicinella without opercular valves,--with the
opercular membrane thickened down to the basis,--and with the shell,
excepting the few last-formed basal zones of growth, almost wholly
removed by the breakage of its upper end; this remnant of a shell,
however, presenting some strong points of resemblance to Coronula.