point broken and lost, but it must have run up between the terga for
more than half their length; basal portion inflected at nearly right
angles, and running in between, and close below, the linear basal
segments of the scuta, so as almost entirely to cut off internally the
peduncle and capitulum. This lower inflected and imbedded portion, or
disc, gradually widens towards its further end, which is, at least, four
times as wide as the upper part of the carina, and is deeply excised,
but to what exact extent I cannot state, as the specimen was much
broken. On each side of this elongated triangular disc, there is a
slight shoulder corresponding to the ends of the basal segments of the
scuta; and on the upper surface of each shoulder, there is a small tooth
or projection. The middle part of the disc is barely calcified, and is
transparent.
_Peduncle_, rather longer than, and not above half as wide as, the
capitulum; the latter being nearly 2/10ths of an inch in length: the
membrane of the peduncle is thin, naked and structureless.
_Mouth._--Labrum highly protuberant in the upper part, with a row of
beads on the crest. Palpi small, with few bristles. _Mandibles_, with
the whole inferior part, very narrow; three teeth very sharp, with a
slight projection, perhaps, marking the place of a fourth tooth;
inferior angle ending in the minutest point; first tooth as far from the
second, as the latter from the inferior angle. _Maxillæ_ with a _broad_
shallow notch; inferior angle much rounded, bearing only four or five
pair of spines.
_Cirri._--First pair apparently remote from the second pair; all five
posterior pair lost; first pair short, with the rami unequal by about
two segments; segments clothed with several transverse rows of bristles;
terminal segments blunt.
3. DICHELASPIS PELLUCIDA. Pl. II, fig. 7.
_D. valvarum singularum acuminibus superioribus et inferioribus vix
intersecantibus: scutorum segmento basali multo angustiore quam
segmentum occludens; longitudine ferè dimidiâ: tergis bipenniformibus,
margine integro, manubrii acumine ad carinam flexo._
Valves with the upper and lower points of the several valves only just
crossing each other. Scuta with the basal segment much narrower than the
occludent segment, and about half as long as it. Terga like a
battle-axe, with the edge smooth, and the point of the handle bent
towards the carina.
Mandibles with four teeth; caudal appendages twice as long as the
pedicels of the sixth cirrus.
Indian Ocean; attached to a sea-snake.
This species comes very close to the _D. Grayii_, which likewise was
attached to a snake; but I cannot persuade myself, without seeing a
graduated series, that the differences immediately to be pointed out can
be due to ordinary variation. I am much indebted for specimens to the
kindness of Mr. Busk.
_General Appearance._--The membrane of the capitulum and peduncle is
surprisingly thin and pellucid, so that the ovarian tubes within the
peduncle can be traced with the greatest ease. The valves are small, the
apices only just crossing each other, and are composed of yellow
chitine, with mere traces of calcification. The capitulum is pointed,
oval, .15 of an inch long; the peduncle is narrow, and fully twice as
long as the capitulum.
_Scuta._--The two segments stand at right-angles to each other; the
basal segment is linear and pointed, fully half as long, but only one
third as wide, as the occludent segment. The point of junction of the
two segments is wider than the rest of the basal segment. This latter
segment lies some little way above the top of the peduncle. The
occludent segment is bluntly pointed; it is directed a little inwards
from the edge of the orifice towards the terga; the apex reaches up just
above the slightly reflexed lower point of the terga. The adductor
muscle is fixed under the point of junction of the two segments.
The _Terga_ are battle axe-shaped, with the blade part very prominent,
smooth-edged; behind the blade there is a short upwardly-turned
prominence. The lower point of the handle of the axe, is bent towards
the carina. The tergum, measured in a straight line, equals in length
two thirds of the occludent segment of the scutum, the handle being
rather narrower than this same segment.
The _Carina_ is extremely narrow and much bowed; the apex reaches up
only to just above the lower bent points of the terga. The basal end is
rectangularly inflected, and stretches internally nearly across the
peduncle; it consists (fig. 7 _a_) of a triangular disc of yellow thin
membrane, four or five times as wide as the upper part of the valve; the
end of this disc is hollowed out; its edges are thickened and calcified,
and hence, at first, instead of a disc, this lower part of the carina
appears like a wide fork; the tips of the prongs stretch just under the
tips of the basal segments of the scuta.
_Peduncle._--Its narrowness and transparency are its only two remarkable
characters.
_Mouth._--All the parts closely resemble those of _D. Grayii_, but being
in a better state of preservation I will describe them. The labrum is
highly bullate, with a row of minute teeth on the crest, placed very
close together in the middle. Palpi small, thinly clothed with spines;
mandibles extremely narrow, hairy, with four teeth, but the lower tooth
is so close to the inferior angle, as only to make the latter look
double. Maxillæ, with a very deep broad notch, dividing the whole into
two almost equal halves; in the upper part there are three main spines.
_Cirri._--The first pair are placed at a considerable distance from the
second pair; they are short with equal rami, and rather broad segments
furnished with a few transverse rows of bristles. The five posterior
cirri have singularly few, but much elongated segments, bearing four
pair of spines: the two rami of the second pair are alike, and differ
only from the posterior cirri in a few of the basal segments having a
few more spines.
The _Caudal Appendages_ are twice as long as the pedicels, and nearly
half as long as the whole of the sixth cirrus; they have a small tuft of
long thin spines at their ends, and a few in pairs, or single, along
their whole length; at first I thought that they were multi-articulate,
but after careful examination I can perceive no distinct articulations;
I have seen no other instance of so long an appendage without
articulations.
_Diagnosis._--This species differs from _D. Grayii_ in all the valves
being shorter, so that their points only just cross each other; but
this, I conceive, is an unimportant character. In the scuta, the basal
segment is here narrower, but the point of junction of the two segments
wider than in that species; in the terga, the edge of the axe is smooth
instead of being crenated, and the handle and the point behind are of a
rather different shape; in the carina the imbedded basal disc has not
shoulders and small teeth, as in _D. Grayii_. Notwithstanding these
differences, I should not be much surprised if the present form were to
turn out to be a mere variety.
4. DICHELASPIS LOWEI. Pl. II, fig. 8.
_D. scutorum segmento basali angustiore quam occludens segmentum,
longitudine ferè 4/5: tergorum parte inferiori duplo latiore quam
occludens scutorum segmentum._
Scuta with the basal segment narrower than the occludent segment, and
about four-fifths as long as it. Terga with the lower part twice as wide
as the occludent segment of the scuta.
Mandibles with four teeth; segments of the three posterior cirri with
eight pair of main spines.
_Hab._--Madeira; attached to a rare Brachyourous Crab,
discovered by the Rev R. T. Lowe. Very rare.
_General Appearance._--Capitulum much compressed, sub-triangular, formed
of very thin membrane; valves imperfectly calcified, and thin.
_Scuta_ formed of two narrow plates placed at about an angle of 50° to
each other, and united at the umbo by a non-calcified flexible portion.
The primordial valve is situated at this point, but chiefly on the
occludent segment. The occludent segment is about twice as wide and
about one fifth longer than the basal segment, which latter is rather
sharply pointed at its end. The occludent segment is slightly arched, a
little narrowed in on the occludent margin close to the umbo; its upper
end is broad and blunt; it runs throughout close to the edge of the
orifice of the sack, and its longer axis is in the same line with that
of the terga. Close to the umbones, on the under side of the basal
segment, there is, on each valve, a longitudinal calcified fold, serving
as a tooth.
_Terga_ broad, with a deep notch corresponding to the apex of the
occludent segment of the scuta; the part beneath the notch is of nearly
the same width throughout, and is twice as broad as the occludent
segment of the scuta; it has its basal angle very broad and blunt. The
entire length of the terga equals two thirds of that of the occludent
segment of the scuta; occludent margin simply and slightly curved.
The _Carina_ is of nearly the same width throughout, with the upper part
rather the widest, and the apex blunt; within _convex_; it extends up
between three fourths of the length of the terga, terminating downwards
in a fork with very sharp prongs, standing at right-angles to each other
(fig. 8 _a_.) The fork, measured from point to point, is thrice as wide
as, and measured across at the bottom of the prongs it is wider than,
the widest upper part of the valve,--a resemblance being thus shown with
the triangular notched disc in _D. Grayii_. The points of the prong
extend under about one fourth of the length of the basal segments of the
scuta.
_Peduncle_ rather longer than the capitulum, which, in the largest
specimen, was 2/10ths of an inch in length; peduncle narrow, close under
the capitulum; membrane thin and structureless. The larger specimen had
almost mature ova in the lamellæ.
_Mouth._--Labrum with a few bead-like teeth on the crest, distant from
each other even in the central part; palpi rather small, moderately
clothed with bristles.
_Mandibles_, with four teeth; the inferior angle blunt and broad,
showing, apparently, a rudiment of a fifth tooth; the first tooth is as
far from the second, as is this from the inferior angle; second, third,
and fourth teeth very blunt, whole inferior part of mandible not much
narrowed. Maxillæ small, with a small notch under the three upper
spines, which are followed by five or six pair, nearly as large as the
upper spines.
_Cirri._--First pair remote from the second; their rami nearly equal,
and about one third of the length of the rami of the second cirrus;
thickly clothed with bristles: rami of the second cirrus of equal
thickness, but little shorter than those of the sixth cirrus; the three
or four basal segments of the anterior ramus are thickly clothed with
spines; the other segments, and all the segments on the third pair,
resemble the segments of the three posterior pair. These latter are
elongated, not protuberant, and support eight pairs of spines with very
minute intermediate spines; those in the dorsal tufts are numerous and
long.
_Caudal Appendages_ nearly as long as the pedicels of the sixth cirrus;
oval, moderately pointed, with their sides, for one fourth of their
length, thickly clothed with long very thin spines.
_Affinities._--In the form of the scuta and of the carina this species
is most nearly allied to _D. Grayii_ or _D. pellucida_, in the form of
the terga to _D. Warwickii_.
5. DICHELASPIS ORTHOGONIA. Pl. II, fig. 10.
_D. scutorum basali segmento angustiore quam occludens segmentum;
longitudine ferè dimidiâ; duorum segmentorum junctione calcareâ:
tergorum prominentiis marginalibus inæqualibus quinque: carinâ deorsum
in parvo calyce lunato terminatâ._
Scuta with the basal segment narrower than the occludent segment, and
about half as long as it; junction of the two segments calcified. Terga
with five unequal marginal projections. Carina terminating downwards in
a small crescent-formed cup.
Maxillæ with the inferior part of edge much upraised.
Hab. unknown; associated with _Scalpellum rutilum_, apparently
attached to a horny coralline. British Museum.
The specimens are in a bad condition, not one with all the valves in
their proper positions, and most of them broken; animal’s body much
decayed and fragile.
_General Appearance._--Capitulum apparently much flattened; valves
naked, coloured reddish, separated from each other by thin structureless
membrane.
The _Scuta_ consist of two bars placed at right-angles to each other,
with the point of junction fully as wide as any part of the basal
segment, and perfectly calcified; the primordial valve lies at the
bottom of the occludent segment. The basal segment is equally narrow
throughout, and very slightly concave within; the occludent segment
widens a little above the junction or umbo, and then keeps of the same
width to the apex, which is obliquely truncated; internally this segment
is concave; externally it has a central ridge running along it; the
occludent segment is twice as long and twice as broad as the basal
segment. Both segments are a little bowed from their junction to their
apices.
_Terga._--These are of a singular shape; they are about three-fourths as
long as the occludent segment of the scuta, and in their widest part, of
greater width than it. They consist of four prominent ridges proceeding
from the umbo, and united together for part only of their length, and,
therefore, ending in four prominences; one of these, the longest, has
the same width throughout, and forms the basal point; a second, very
small one, is seated high up on the carinal margin just above the apex
of the carina; the third and fourth, are nearly equal in length, and
project one above the other on the scutal margin. There are two
occludent margins, meeting each other at right angles, and forming a
prominence, as in Lepas; and this gives to the margin of the valve the
five prominences. The whole valve internally is flat; externally, it is
ridged as described.
_Carina_ (fig. 10, _a_, _b_), much bowed, narrow, long; externally, the
central ridge is quite flattened; internally, slightly concave, but
scarcely so towards the lower part, which is narrow; the upper part
widens gradually, and the apex is rounded. The basal embedded portion is
as wide as the uppermost part, and forms a cup, unlike anything else
known: the outline of this cup is semi-oval and crescent-formed; it is
moderately deep; it is formed by the external lamina of the carina
bending rectangularly downwards and a little outwards, whereas the inner
lamina of the lower part (which is slightly concave), is continued with
the same curve as just above, and forms the concave chord to the
semi-oval rim of the cup. This cup, I believe, lies under the points of
the basal segments of the scuta.
_Peduncle_ unknown, probably short.
_Length_ of capitulum, above 2/10ths of an inch.
_Mouth._--Labrum with the upper part highly bullate, and produced into a
large overhanging projection; crest with a row of rather large bead-like
teeth; _palpi_ small, their two sides parallel, very sparingly covered
with long bristles.
_Mandibles_, narrow, produced, with four teeth, and the inferior angle
produced into a single strong spine: the distance between the tips of
the first and second teeth almost equals that between the tip of the
second tooth and of the inferior angle.
_Maxillæ_ with three large upper unequal spines, beneath which, there is
a deep and wide notch (bearing one spine), and the inferior part
projects highly, bearing three or four pairs of spines, and is, itself,
obscurely divided into two steps.
_Outer Maxillæ_, very sparingly covered with bristles; outline,
hemispherical.
_Cirri._--The rami of the five posterior pair are extremely long, as are
the pedicels; the segments are much elongated, with their anterior faces
not at all protuberant; each bears five pair of very long and thin
spines, with an excessively minute one between each pair; the dorsal
tuft consists of very fine and thin spines. The second cirrus has its
anterior ramus not at all thicker than the posterior ramus; but has an
exterior third longitudinal row of small bristles. First cirrus,
separated by a wide interval from the second pair; very short with the
two rami slightly unequal in length; the segments are broad, and are
paved moderately thickly with spines; the terminal spines not
particularly thick.
_Caudal Appendages_ consist of very small and narrow plates, about half
the length of the pedicels of the sixth cirrus, with a few long spines
at their ends.
This well-marked species, I think, has not more affinity to one than to
another of the previous species: it differs from all, in the junction
between the two segments of the scuta being perfectly calcified; in the
peculiar cup, forming the base of the carina; and lastly, in the
inferior part of the maxillæ projecting.
OXYNASPIS.[33] _Gen. Nov._ Pl. III.
_Valvæ 5, approximatæ: scutorum umbones in medio marginis occludentis
positi: carina rectangulè flexa, sursùm inter terga extensa, termino
basali simpliciter concavo._
Valves 5, approximate; scuta with their umbones in the middle of the
occludent margin; carina rectangularly bent, extending up between the
terga, with the basal end simply concave.
[33] From [Greek: oxunô], to sharpen, and [Greek: aspis], a
shield or scutum.
Mandibles with four teeth; maxillæ notched, with the lower part of edge
nearly straight, prominent; anterior ramus of the second cirrus thicker
than the posterior ramus; caudal appendages, uniarticulate, spinose.
Attached to horny corallines.
I have most unwillingly instituted this genus; but it will be seen by
the following description, that the one known species could not have
been introduced into Lepas or Pæcilasma, without destroying these
genera, although it has a close general resemblance with both. As far as
the valves are concerned, it is more nearly related to Lepas than to
Pæcilasma; but taking the entire animal, its relation is much closer to
the latter genus than to Lepas: it differs from both these genera in the
manner of growth of the scuta, which is both upwards and downwards, the
primordial valve being situated in nearly the middle of the occludent
margin. In this respect, and in the shape of the carina and terga, there
is an almost absolute identity with Scalpellum; I may, however, remark
that in Scalpellum, the scuta first grow downwards, and afterwards in
most of the species upwards, whereas here from the beginning, the growth
is both upwards and downwards. In the mouth and cirri, there is rather
more resemblance to Scalpellum than to Pæcilasma and Lepas: in habits,
also, this genus agrees with Scalpellum, and if it had possessed a lower
whorl of valves, it would have quite naturally entered that genus. It is
unfortunate, that so insignificant and poorly characterised a form
should require a generic appellation. In natural position, it appears to
lead from Scalpellum through Pæcilasma to Lepas.
1. OXYNASPIS CELATA. Pl. III, fig. 1.
Madeira; attached in numbers to an Antipathes; Rev. R. T. Lowe.
Mus., Hancock.
_General Appearance._--The capitulum is rather thin, and broad in
proportion to its length; it seems always entirely covered by the horny
muricated bark of the Antipathes, and hence externally is coloured rich
brown and covered with little horny spines. The membrane over the valves
is very thin, and is with difficulty separated from the Antipathes; it
has, I believe, no spines of its own. The corium lining the peduncle is
a fine purple. All the individuals are attached to the coralline, with
their capitulums upwards in the direction of the branches, and in this
respect fig. 1. is erroneous.
The valves, when cleared of the bark, are white, or are strongly tinged
with pinkish-orange. The upper parts of the scuta and terga are plainly
furrowed in lines radiating from their umbones; hence their margins are
serrated with blunt teeth; their surfaces, moreover, are sparingly
studded with small calcareous points.
_Scuta_ (fig. 1, _a_), sub-triangular, with the lower part rounded and
protuberant, the upper produced and pointed. The umbo is situated in the
middle of the occludent margin, instead of at the rostral angle, as in
the foregoing genera. The occludent margin is straight, and is bordered
by a narrow step or ledge, formed of transverse growth-ridges, and
therefore has its edge serrated: the rostral angle is often slightly
produced into a small projection. The basal margin is short, and forms
an angle above a rectangle with the occludent margin: the tergal margin
is straight; the carinal margin is rounded, protuberant, and of unusual
length compared to the basal margin. The surface of the valve is convex
near the umbo; and beneath there is a large deep hollow for the adductor
muscle.
_Terga_ (fig. 1, _b_) large, flat, triangular, as long as the scuta or
the carina, all three valves being nearly equal in length; occludent
margin straight, or slightly arched, basal angle broad, not very sharp.
_Carina_ short (fig. 1, _c_, drawn rather too long), deeply concave,
rectangularly bent, with the lower part not quite as long as the upper,
and a little wider: the basal margin is truncated, rounded, and slightly
sinuous. The umbo is situated at the angle, and therefore nearly
central. The umbo of the terga, I may add, is in the same place, as in
Lepas.
The _peduncle_ is very short and narrow, and is, I believe, without
spines; it is enveloped by the bark of the Antipathes. The capitulum in
the largest specimens was .2 of an inch in length.
_Filamentary Appendages_, apparently none.
_Mouth_, with the orifice rather inclined abdominally.
_Labrum_, with the upper part extremely protuberant, forming a
projecting horn; no teeth on the crest. Palpi rather small, with only a
few bristles at the end.
_Mandibles_, with four teeth and the inferior angle pointed: first
tooth as far from the second, as is the latter from the inferior angle;
in one specimen, on one side, there were five teeth.
_Maxillæ_ with three great spines at the upper angle, beneath which a
deep notch, and with the inferior part much upraised; this lower part
rather rounded at both corners, with the upper spines longer than the
lower.
_Outer Maxillæ_, with the bristles continuous in front; externally,
slightly protuberant, with a tuft of bristles longer than those on the
front side. Olfactory orifices apparently not protuberant; but all the
specimens were in a bad state.
_Cirri._--Prosoma very little developed. First cirrus very far removed
from the second. The three posterior cirri are straight and long; the
segments are elongated and bear four or five pairs of very long spines,
with a single minute intermediate spine between each pair; dorsal tufts,
with long spines. First cirrus, rami unequal by two or three segments,
and thickly covered with spines; the first cirrus is short compared to
the second, owing to the length of the pedicel of the latter, though the
longer ramus of the first, nearly equals the shorter ramus of the second
pair. Second cirrus, with its anterior ramus shorter by two or three
segments than the posterior ramus, and thicker than it, with the
segments covered like brushes with bristles; posterior ramus, and both
rami of the third cirrus, a little more thickly clothed with bristles
than are the three posterior cirri.
_Caudal Appendages_, minute, broadly oval, with six or seven long
bristles on their summits.
_Genus_--CONCHODERMA. Plate III.
CONCHODERMA. _Olfers._ Magaz. der Gesellsch. Natuforsch. Freunde
zu Berlin, Drittes Quartel, 1814.[34]
LEPAS. _Linnæus._ Systema Naturæ, 1767.
BRANTA. _Oken._ Lehrbuch der Naturgeschichte, Th. 2, p. 362, 1815.
MALACOTTA et SENOCLITA. _Schumacher._ Essai d’un Nouveau Syst. des
Habitations des Vers., 1817.
OTION et CINERAS. _Leach._ Journal de Phys., vol. lxxxv, p. 67,
July, 1817.
GYMNOLEPAS. _De Blainville._ Dict. des Sci. Nat., Art. Mollusca,
1824.
PAMINA. _J. E. Gray._ Annals of Philosophy, vol. x, (Second
Series,) August, 1825.[35]
[34] The general title to the volume, containing four Quarterly
parts, is dated 1818; but as in the ‘Journal de Physique,’ for
July, 1817, the editor refers to Conchoderma, the Quarterly Part
containing this genus must have appeared before 1818: Lamarck
gives the year 1814 as the date of the paper in question, and I
have accordingly followed him. From a similar reference by the
editor, it appears that Schumacher’s volume appeared before the
number of the ‘Journal de Physique’ containing Leach’s Paper.