points of the terga; with its lower end either truncated or produced
into a deeply imbedded disc. Scuta nearly oval, with their umbones at
the rostral angle.
Mandibles with four teeth; maxillæ notched, with the lower part of edge
prominent; anterior ramus of the second cirrus not thicker than the
posterior ramus; caudal appendages uniarticulate, spinose.
Generally attached to Crustacea.
I have already given my reasons for instituting and separating this
genus from Lepas; as far as the capitulum is concerned, the differences
between these genera certainly appear trivial; they consist in the
carina not extending up between the terga, and in the lower end being
either truncated, or produced into an imbedded disc: the terga have a
single occludent margin. The included animal’s body differs in more
important respects; for both mandibles and maxillæ are very distinct;
the cirri of some of the species also differ; and the caudal appendages
are here always spinose: there are no filamentary appendages: and
lastly, the habits are different.
The genus may be divided into two sections, firstly, _P. Kæmpferi_ and
_P. aurantia_, which have their carinæ basally truncated, the basal
angles of their terga cut off, and the anterior rami of their second
cirri shorter than the posterior rami; and, secondly, _P. crassa_, _P.
fissa_, and _P. eburnea_, which in these several respects are otherwise
characterised. The _P. eburnea_, however, differs rather more from _P.
crassa_ and _P. fissa_, than these two do from each other; but certainly
not enough to allow of the retention of Mr. Hinds’ genus of Trilasmis.
_P. crassa_, in an especial degree, connects together all the forms.
_General Appearance._--Capitulum oval, more or less produced, flat or
gibbous; formed of three, five, or seven approximate valves; the lesser
number arising from the abortion of the terga, and the greater number
from the scuta being divided into two segments. Valves moderately thick,
either white or reddish, smooth or striated, and sometimes partly
covered by membrane, bearing minute spines. _Scuta_ oval, of varying
proportions; the basal margin is generally narrow, and blends into the
carina-tergal margin; the internal basal rim generally is well
developed, sometimes with, and sometimes without internal teeth beneath
the umbones. In _P. eburnea_, and sometimes in _P. crassa_, there is a
line of apparent fissure, and in _P. fissa_ of actual disseverment,
running from the umbo to the apex of each scutum, nearly in the line in
which a ridge extends in Lepas: the primordial valves of the scuta in
these three species, are seated at the basal angles of the lateral and
larger segments. The positions of the primordial valves, and the
direction of growth in the calcified valves, are, in all the species,
the same as in Lepas. In several of the species attached to Crustacea,
the two scuta are unequally convex, which is caused, as was pointed out
to me by Mr. Gray, by that valve which lies close and nearly parallel to
the body of the crab, being least developed. The _Terga_ are either
quite absent, or rudimentary as in _P. crassa_, or pretty well developed
as in the other species: the occludent margin is single, and not double
as generally in Lepas; the basal angle is either pointed or truncated.
The _Carina_ varies considerably in shape, but never extends up between
the terga, nor ends downwards in a fork; in the first two species it is
truncated; in the others, it terminates in a deeply-imbedded oblong
disc, which in _P. eburnea_ seems almost entirely (but of course not
quite) to separate the inside of the capitulum from the peduncle; a
similar separation is effected in _P. fissa_, where the imbedded disc is
small, by two large teeth on the internal basal rims of the two scuta.
The carina is always narrow, and either solid internally or very
slightly concave.
_Peduncle_, is very short and narrow; the membrane is generally ringed
with thicker, yellower portions, and often bears very minute spines.
_Size._--All the species are small, with a capitulum not exceeding half
an inch in length.
_Filamentary Appendages._--None.
_Mouth._--Labrum generally considerably bullate in the upper part, with
a row of teeth on the crest. The _mandibles_ have four teeth, with the
inferior point narrow and spine-like, or rudimentary and absent. The
_maxillæ_ have, under the two or three upper great spines, a deep notch
itself bearing spines; beneath this, the lower part is straight and
considerably prominent, Pl. X, fig. 15. Outer maxillæ are covered on
their inner sides continuously with spines.
_Cirri._--The first pair is sometimes seated very distant from the
second. The arrangement of the spines on the posterior cirri varies, to
an unusual degree within the limits of the same genus. We have either
the ordinary structure of anterior pairs, with single fine intermediate
spines (as in _P. Kæmpferi_ and _aurantia_), or we have the pairs
increased by one or two additional longitudinal lateral rows, as in _P.
eburnea_; or we have the front spines forming a single transverse row,
as in _P. crassa_ and _P. fissa_, Pl. X, fig. 29, _a_. The segments in
none of the species are protuberant; the anterior ramus of the second
cirrus does not seem to be thicker than the posterior ramus, as is
usually the case. The rami of the second, and of most of the other
cirri, are unequal in length,--the anterior ramus, contrary to the
ordinary rule, being longer in _P. eburnea_, _P. fissa_, and _P.
crassa_, than the posterior ramus by several segments; I have hitherto
observed this inequality only in the sessile genus Chthamalus.
The _Caudal Appendages_ are small, uniarticulate, and always furnished
with bristles.
_Distribution._--Four out of the five species live attached to
Crustacea in the European and Eastern warmer temperate and
tropical oceans; the fifth species was found attached to the
dead spines of an Echinus, off New Guinea. It is probable that
several more species will be hereafter discovered.
1. PÆCILASMA KÆMPFERI. Pl. II, Fig. 1.
_P. valvis 5; carinæ basi truncatâ et cristatâ: scutorum dentibus
internis umbonalibus fortibus: tergorum acumine basali truncato,
margini occludenti pæne parallelo._
Valves 5; carina with a truncated and crested base; scuta with strong
internal umbonal teeth; terga with the basal point truncated, almost
parallel to the occludent margin.
Maxillæ with short thick spines in the notch under the two upper great
spines; caudal appendages with scattered bristles on their summits, and
along their whole outer margins.
Japan; attached, in great numbers, to the upper and under sides
of the _Inachus Kæmpferi_ of De Haan, a slow-moving brachyourous
crab, probably from deep water. British Museum.
_General Appearance._--Capitulum rather compressed, narrow, and
produced. Valves white, tinged with orange, smooth, moderately thin,
occasionally with faint traces of striæ radiating from the umbones.
_Scuta_, apex pointed, with a very slight ridge running to the umbo;
basal margin equalling two thirds of the length of the terga, with an
internal basal rim; on the under side of each valve, beneath the umbo,
there is a strong tooth. Out of the numerous specimens, all excepting
one had their scuta unequally convex, with their occludent margins
unequally curved, that of the more convex valve at the umbo, curling
beyond the medial line. The basal end of the carina is, likewise,
slightly curved laterally, and always turns towards the more convex
valve. This inequality, as Mr. Gray pointed out to me, depends on the
position of the specimens; the flatter side lying close to the carapace
of the crab. _Terga_, flat, oblong, nearly rectangular; occludent margin
straight; basal angle, truncated, almost parallel to the occludent
margin; in width, three or four times as wide as the carina. _Carina_,
(fig. 1, _a_) short, narrow, slightly curved, upper part broadest, with
the apex rounded, only just passing up between the basal broad ends of
the terga; externally carinated, internally very slightly concave; basal
end abruptly truncated, crested, not deeply imbedded in the membrane of
the peduncle.
_Peduncle_, barely as long as the capitulum, apparently (for specimens
dry and much shrunk) narrow, surrounded by rings or folds of thicker
yellowish membrane, of which the upper ones retain moderately long
spines; low down these rings become confluent; whole surface finely
dotted, dots largest on the rings.
_Mouth._--Labrum highly bullate in the upper part, with a row of teeth
on the crest; mandibles with four teeth, the fourth close to the
inferior apex, which is very little developed, sometimes making the
fourth tooth appear simply bifid. Maxillæ with two large spines on the
upper angle, beneath which there is a large depression, bearing one
rather long and thick, and four short and thick, spines; inferior
upraised part with a double row of longer and thinner spines.
_Cirri._--Posterior cirri with segments bearing five pairs of spines, of
which the lowest pair is very minute; intermediate spines minute; spines
of the dorsal tuft thin, of nearly equal size; segments not at all
protuberant, elongated. First cirrus, standing far separated from the
second (as in Scalpellum), with its nearly equal rami rather above half
as long as those of the second cirrus. Second cirrus with anterior ramus
not thicker, and scarcely more thickly clothed with spines, than the
posterior ramus, but shorter than it by three or four segments; the
spines not forming a very thick brush on the anterior ramus. Both rami
of third cirrus with a longitudinal row of minute spines, parallel to
the main pairs. Between the bases of the pedicels of the first pair of
cirri, there are two closely approximate, conical flattened
protuberances, like the single one to be described in Ibla.
_Caudal Appendages_, about one third of the length of the pedicel of the
sixth cirrus, with some moderately long and strong spines at the end,
and down the whole outer sides.
_Ova_, much pointed. _Penis_, hairy.
_Size._--Capitulum in largest specimens half an inch long.
2. PÆCILASMA AURANTIA. Pl. II, Fig. 2.
_P. valvis 5; carinæ basi truncatâ: scutis ovatis, margine basali
perbrevi, dentibus parvis, internis, umbonalibus instructo: tergorum
acumine basali perobliquè truncato._
Valves 5; carina with a truncated base; scuta oval, with the basal
margin very short, furnished with small internal umbonal teeth; terga,
with the basal point very obliquely truncated.
Maxillæ with fine spines in the notch under the three great upper
spines; caudal appendages with scattered bristles on their summits, and
along only the upper part of their outer margins.
Madeira; found by the Rev. R. T. Lowe, attached to the rare
_Homola Cuvierii_, probably a deep-water crab. British Museum.
_General Appearance._--This species so closely resembles _P. Kæmpferi_,
that it is superfluous to describe it in detail; and I will indicate
only the points of difference. When the valves have been well preserved,
they are of fine pale orange colour, and hence the name above given,
which was proposed by the Rev. R. T. Lowe.
_Scuta_, with the internal umbonal teeth small; basal internal marginal
rim very prominent, furrowed within; basal margin short, (only equalling
half the length of terga), owing to the great curvature of the lower
part of the carino-tergal margin; hence, the outline of the scuta is
almost pointed oval. I saw no appearance of inequality in the two sides.
_Terga_, rather smaller in proportion to the scuta, than in _P.
Kæmpferi_, with the basal end very obliquely truncated, so as to appear
at first simply pointed, not parallel to the occludent margin; apex
considerably more pointed and produced than in the foregoing species.
_Carina_, almost of equal narrowness throughout, barely concave within;
lower end triangular, abruptly truncated, and not crested.
_Primordial valves_ very plain, with the usual hexagonal structure:
those of the terga, rounded at both ends, instead of being square, as in
the mature calcified valves.
_Peduncle_ short, narrow, not half as long as the capitulum; paved with
minute equal beads, as in the genus Dichelaspis.
_Mouth._--Mandibles with the fourth tooth very small; inferior angle
rudimentary. Maxillæ, with three great upper spines, beneath which there
is a deep notch bearing some delicate spines; inferior upraised part, as
in _P. Kæmpferi_.
_Cirri._--Rami of first cirrus hardly more than one third as long as the
rami of the second cirrus, which latter rami are unequal in length by
only two segments; the posterior ramus being the longer one.
_Caudal Appendages_, with only two or three lateral bristles, besides
those on the summit.
_Size._--Capitulum, three to four tenths of an inch long.
_General Remarks._--This species has the closest general resemblance to
_P. Kæmpferi_, and is evidently a representative of it. On close
examination, however, almost every part differs slightly; the chief
points being the narrowness of the basal margin of the scuta; the
obliqueness of the truncated basal end of the terga and the sharpness of
the upper end; the rudimentary state of the inferior angle of the
mandibles; the character of the spines on the maxillæ; the proportional
lengths of the cirri, and the fewness of the spines on the outer sides
of the caudal appendages. The fact of Madeira having this Pæcilasma, a
representative both in structure and habits of a Japan species, is
interesting, inasmuch, as I am informed by Mr. Lowe, that some of the
Madeira fishes are analogues of those of Japan.
3. PÆCILASMA CRASSA. Pl. II. Fig. 3.
ANATIFA CRASSA. _J. E. Gray._ Proc. Zoolog. Soc., 1848, p. 44,
Annulosa, Tab. iii, figs. 5, 6.
_P. valvis 5; carinæ termino basali in discum parvum infossum producto:
scutis convexis, dentibus internis umbonalibus nullis: tergis pæne
rudimentalibus, vix carinâ latioribus._
Valves 5; carina with the basal end produced into a small imbedded disc;
scuta convex, without internal umbonal teeth; terga almost rudimentary,
scarcely broader than the carina.
Spines on the segments of the posterior cirri arranged in single
transverse rows.
Madeira; attached to the _Homola Cuvierii_, Rev. R. T. Lowe.
British Museum.[31]
_General Appearance._--Capitulum highly bullate, or thick. Valves rather
thick, opaque, either pale or dark flesh-red, smooth, yet rather plainly
striated from the umbones. There are a few very minute spines on the
membranous borders of the valves.
_Scuta_ highly convex, broadly oval, apex broad rounded; basal margin
narrow, much curved; no internal, umbonal teeth; basal internal rim
strong, running up part of the occludent margin. A slightly prominent
ridge, either rounded or angular, but in one specimen a narrow depressed
fissure-like line, runs parallel to the occludent margin and ends near
the apex in a slight notch; this fact is of interest in relation to the
structure of the scuta in _P. eburnea_ and _P. fissa_. The scuta are
either equally or very unequally convex; in the latter case, the
occludent margin of one valve is curled, so that its umbo is not quite
medial.
[31] It is stated, in ‘Zoolog. Proc.,’ (1848, p. 44,) that this
species was attached to a gorgonia, from Madeira; I cannot but
suspect that there has been some confusion with the _Oxynaspis
celata_ from Madeira, which is thus attached.
_Terga_, minute, almost rudimentary, scarcely broader than the carina,
and half as long as the chord of its arc; carinal margin slightly
curved; scutal margin straight, with a slight prominence fitting into a
notch in the scuta; basal end bluntly pointed.
_Carina_, (fig. 3, _a_) rather shorter than the scuta, extending up only
to the basal ends of the terga; moderately curved; apex moderately
sharp; middle part broadest, externally carinated; internally not
concave, with the inner lamina of shell, at the basal end, produced into
a very small oblong disc or tooth, which is only as wide as the
narrowest upper part of the valve. The exterior keel does not extend on
to this disc, which is slightly constricted at its origin.
_Peduncle_ very short, narrow, ringed, and apparently without spines.
_Size._--Capitulum four tenths of an inch long.
The following parts of the animal are described from some small and not
well preserved specimens from Madeira, which I owe to the kindness of
Mr. Lowe.
_Mouth._--Labrum highly bullate in the upper part, with large, inwardly
pointed, unequal teeth. Mandibles, with four large, pointed, equal-sized
teeth, with the inferior angle very narrow, acuminated like a single
spine. Maxillæ, with three (?) large upper spines, of which the middle
one is extremely strong and long, beneath which, there is a deep notch
with a single strong spine, and with the whole inferior part square and
much upraised, so as to stand on a level almost with the tips of the
great upper spines.
_Cirri_ in a miserable state of preservation; first cirrus short, second
cirrus with rami unequal, and I suspect the anterior one the longest;
some of the other cirri also have unequal rami. The segments of the
posterior cirri are not protuberant, they have on their anterior faces a
single transverse row of bristles: in the upper segments, some of the
spines in each dorsal tuft (which is much spread out), are _much_
thicker, though rather shorter than those on the anterior face. This
peculiar structure is common to all five posterior cirri.
_Caudal Appendages._--I can only say that they are spinose on their
summits.
_Affinities._--This species is allied to _P. eburnea_ in the rudimentary
condition of its terga; in the disc-shaped basal end of its carina; and
in the presence in some specimens, of a fissure-like line on the scuta
parallel to their occludent margins. Its affinity, however, is closer to
_P. fissa_, as is more especially shown by the remarkable arrangement of
the spines on the five posterior cirri.
4. PÆCILASMA FISSA. Pl. II, Fig. 4.
_P. valvis 7; scuto utroque è duobus juxtapositis segmentis formato;
segmento altero intus dentato: tergis brevibus, ter aut quater carinâ
latioribus: carinæ termino basali in discum parvum angustum infossum
producto._
Valves 7; each scutum being formed of two closely approximate segments;
of which one is internally toothed: terga short, three or four times as
wide as the carina: carina with the basal end produced into a small,
narrow, imbedded disc.
Spines on the segments of the posterior cirri arranged in single
transverse rows.
Philippine Archipelago; Island of Bohol; parasitic on a spinose
crab, found under a stone at low water; single specimen, in
Mus., Cuming.
_General Appearance._--Capitulum gibbous, broadly oval, nearly a quarter
of an inch long. Valves white, smooth, moderately thick, marked by the
lines of growth. The occludent segments of the scuta, and nearly the
whole of the terga, and the whole of the carina, enveloped in
lemon-yellow membrane, tinged with orange, but the specimen had long
been kept dry.
_Scuta_ formed of two, apparently always separate, segments, closely
united, so that externally their separation is hardly visible, and does
not allow of movement; the fissure thus formed runs almost in the line
connecting the umbo and apex, (where in most species a ridge extends,)
but a little on the carinal side of it. The occludent segment is
narrowly bow-shaped, pointed at both ends, with the upper end projecting
slightly beyond the apex of the lateral segment, and with the occludent
margin regularly curved from end to end. The lateral segment is large,
of an oval shape, with a narrow strip cut off on one side. Primordial
valves very plain at the umbones of the lateral segments, but none are
visible on the occludent segments; and this makes me believe that these
two pieces are normally parts of a single valve; having only one
specimen of _P. fissa_, I was not able to make out quite certainly
whether the two segments are continuously united at their umbones by a
non-calcified portion of valve, as is certainly the case with
Dichelaspis. The basal margin of the lateral segment is narrow,
inflected, and blends with the carino-tergal margin; it has an internal,
prominent, basal rim, and towards the occludent margin a large,
prominent, internal tooth. This internal basal rim is not parallel to
the outer basal margin, but rises to a point a little way up the
occludent margin, in the same manner as in _P. eburnea_, but in a lesser
degree; in this latter species the peduncle is internally almost cut off
by the large disc of its carina; here, on the other hand, it is
internally almost cut off by these rims and the two large teeth of the
lateral segments of the scuta.
_Terga_ sub-triangular, short, nearly half as broad as long; three or
four times as wide as the carina, and rather wider than the occludent
segment of the scuta; occludent margin single, arched; carinal margin
slightly arched; basal angle bluntly pointed.
_Carina_ very narrow, much arched, running up just between the basal
ends of the terga; exterior ridge enveloped in membrane; heel blunt,
prominent; internally, not concave, even slightly convex, produced at
the lower end into a very narrow, short, imbedded disc, (or rather
tooth,) which is itself a little curved downwards and blunt at the end.
_Peduncle_ very narrow, about half as long as the capitulum; yellow,
finely beaded, plainly ringed, without spines.
_Mouth._--Labrum, with a row of minute teeth; palpi narrow. Mandibles
with all the lower part narrow; of the four teeth, the second and third
are narrow, the fourth is pectinated and placed very close to the
inferior angle, which is produced into a long thin tooth. Maxillæ
unknown.
_Cirri._--First pair lost. The arrangement of the spines on all is most
abnormal, Pl. X, fig. 29: dorsal tuft long, arranged in a transverse
line and seated in a deep notch; in the sixth cirrus, the spines on the
lower segments are fine, those on the upper segments are thick and
claw-like, mingled with some fine spines; in the four anterior cirri the
spines of the dorsal tufts are even thicker and more claw-like. On the
anterior faces, also, of all the segments the spines form a single row;
they are shorter than those composing the dorsal tuft; hence the spines
on each segment are arranged in a circle, interrupted widely on the two
sides: this arrangement is common to all five posterior cirri. Second
cirrus, with the _anterior_ ramus one third longer and thinner than the
posterior ramus (this is the reverse of the usual arrangement); this
longer ramus equals in length the sixth cirrus. Third cirrus, with the
anterior ramus considerably longer than the posterior ramus; in the
three posterior pair of cirri, also, the anterior rami are a little
longer than the posterior: except in length, there is little difference
of any kind between the five posterior pair of cirri. Pedicels of the
cirri long; rami rather short; segments elongated, not protuberant.
_Caudal Appendages_ nearly as long as the pedicels of the sixth cirrus,
thickly clothed with very fine bristles, like a camel’s-hair pencil
brush.