A Monograph on the Sub-class Cirripedia (Volume 1 of 2): The Lepadidae; Or, Pedunculated CirripedesDarwin, Charles
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A Monograph on the Sub-class Cirripedia (Volume 1 of 2): The Lepadidae; Or, Pedunculated Cirripedes
Darwin, Charles
Cirripedia; Lepadidae
_Carina_, much bowed, narrow, slightly concave within, (in the Borneo
specimen, rather wider and more concave,) extending up between the terga
for half their length, terminating downwards in a rectangularly
inflected, deeply imbedded, oblong, rather wide, flat disc, at its
extremity more or less deeply notched. This disc is externally smooth;
internally it sometimes has two divergent ridges on it; it extends
across about two-thirds of the base of the capitulum (fig. 6 _a_, as
seen from beneath, when the peduncle is cut off), to under the middle of
the basal segments of the scuta.
_Peduncle_, narrow, flattened; united to the capitulum some little way
below the scuta; about as long as the capitulum; the membrane of which
it is composed is thin, externally studded with bluntly conical beads of
yellowish chitine, of which the largest were 1/2000 of an inch in
diameter; on their internal surfaces these are furnished with a small
central, circular depression, apparently for a tubulus; the arrangement
of the beads varied in concentric zones. Similar conical points on the
capitulum have an internal concave surface about 1/3000 in diameter,
with a central circle 1/12000 in diameter, for the insertion, as I
believe, of a tubulus.
_Size._--The largest specimen had a capitulum a quarter of an inch long.
_Mouth._--Labrum highly bullate; crest with not very minute, blunt
teeth, which towards the middle lie closer and closer to each other, so
as to touch. Palpi rather small, with a few very long bristles at the
apex.
_Mandibles_, narrow, produced, with four teeth, and the inferior angle
tooth-like and acuminated; in one specimen, on one side of the mouth,
the mandible had only three teeth.
_Maxillæ_, small; at the upper angle there are two large spines and a
single small one, beneath which there is a deep notch, and beneath this
a straight but projecting edge, bearing a few moderately large and some
smaller spines. Outer maxillæ sparingly covered with bristles along the
inner margin.
_Cirri._--First pair far removed from the second pair, and not above
half their length; segments rather broad, with transverse rows of
bristles not very thickly crowded together; terminal segments very
obtuse, and furnished with thick spines. The segments of the three
posterior pair have each three or four pair of spines, with a few minute
spines scattered in an exterior, parallel, longitudinal row; dorsal
tufts, with four or five long spines. The second cirrus has its anterior
ramus not thicker, but rather shorter than the posterior ramus; the
former is only a little more thickly clothed with spines, owing to those
in the longitudinal lateral row being longer and more numerous, than is
the sixth pair of cirri. Bristles not serrated.
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