STUDIES
ON ARTHROPODA
I.
BY
Dr. H. J. HANSEN
WITH FOUR COPPER-PLATES
AT THE EXPENSE OF THE RASK-0RSTED FUND
A L 1'' R E D A, K N P F, I n c.
220 West 42nd Street
Nev/ York, N,Y«
1 13.00
COPENHAGEN
PRINTED BY BIANCO LUNO
Ready U'oin the Press January the ^i. 1921.
CONTENTS
Pag.
The Pedipalpi, Ricinulei, and Opiliones (exc. O. Laniatores)
collected by Mr. Leonardo Fea in tropical West Africa
and adjacent Islands (With four Plates) 5
On Stridulation in Crustacea Decapoda 56
On the postembryonic Occurrence of the median "Dorsal Or-
2;an" in Crustacea Malacostraca 66
( 1 v- /^ ^■'
THE PEDIPALPI, RICINULEI, AND OPILIONES
(exc. Op. Laniatores)
coUected by Mr. LEONARDO FEA
in tropical West Africa and adjacent Islands.
(With four Plates.)
SEVERAL years ago Dr. Raffaello Gestro, Director of the
Museo Civico di Storia Naturale di Genova, asked me
to work out the animals of the above-named orders gathered
by that most excellent zoological collector Mr. lyconardo Fea,
who during 1900- — 1902 spent his last years in exploring partly
unhealthy countries in tropical West Africa, viz. Portuguese
Guinea, Kameroon, and French Congo, and besides the islands
of Fernando Poo, St. Thome, Principe, and Annobon in the
Gulf of Guinea; from this voyage Fea returned quite broken
down to Italy and died shortly afterwards in April 1903. With
pleasure I accepted Dr. Gestro's kind offer, as I expected to
tind most interesting animals among the material, but the
main portion of the collection, viz. the Opiliones Laniatores,
I found it necessary to hand over to a colleague, and be-
fore now I could not find the time necessary for the task.
The material to be dealt with in the present paper is in
reality most valuable. It consists of eleven species, but with
two exceptions all are new to science. Furthermore I found
it necessary to establish three new genera, and two among
these are even important. The collection comprises three spe-
cies of Pedipalpi Amblypygi, and one af the forms, living in
nests of white ants, is completely blind ; furthermore two species
of the tribe Tartarides, two species of Cryptostemma and four
species of Opiliones, but two of these belong to the small
studies ou Arthropoda. I.
sub-order Op. C>'phophthalmi. As Tartarides, Ricinulei {Cryp-
tostemma) and Op. C^'phophthalmi are scarce even in the largest
Museums of the world, it is easily seen that the collection is
important out of all proportion to the somewhat low number
of species; the presence of an unknown kind of larval stage
of the Ricinulei highly increases its value. Before concluding
these remarks, I may beg Dr. R. Gestro to accept my sincere
thanks for offering me the material and for his patience as to
the long delay.
ORDER PEDIPALPI
A. Sub-order Amblypygi.
In his monograph (Revision der Tarentuliden Fabr.,
1895) K. Kraepelin accepted three sub-famihes, and in 1902
R. I. Pocock elevated them to the rank of families. Only one
of these families, \'iz. the Phrynida?, was hitherto known from
Africa, and a single well-known form is represented in the col-
lection. But this contains besides two species of the famih'
Charontidae, which hitherto was known only from the Indo-
Australian region and the Galapagos Islands.
It ma}^ be inserted that I am inclined to consider the second
of the two long joints in the mandibular palps as corresponding
to patella plus tibia in Aranese and Pedipalpi Uropygi; in the
descriptions I can therefore follow Kraepelin who named it
tibia.
Titanodamon medius Herbst.
Kraepelin mentioned three varieties, viz. typicns Kraep.,
tibialis Simon, and Johnstoni Pocock; the two last-named va-
rieties had been established as separate species by the authors
Pedipalpi, Ricinulei, and Opiliones.
named, but Kraepelin was certainly right in withdrawing
them. Var. typicus is said to occur from Senegal to the estuary
of the Niger, var. tibialis especially in the Congo region, and
\-ar. Johnstoni in the area between those of the two other forms.
The material comprises specimens belonging to var. typicus
and to var. Johnstoni, but animals from the same locahty vary
not only much according to age in the length of the proximal
one of the three long distal spiniform processes on the upper
margin of the tibia, but between the numerous specimens from
the Isl. of St. Thome, all according to the shape of the frontal
process belonging to var. typicus, a few specimens show a trans-
ition between typicus and Johnstoni as to the setse on the inner
side of the antennae.
Occurrence. — Specimens of var. typicus are to hand
from the following places: Bolama, Portuguese Guinea (near
lat. 12° N.), June — Dec. 1899, 6 specimens; and Isl. of St.
Thome, at Ribeira Palma, o — 300 m above the level of the sea,
Juli — August 1900, 1/ specimens, and 2 small specimens in
June 1900 at the capital of the island.
Specimens of var. Johnstoni were taken at two localities,
\'iz. Basile on Fernando Poo, 400 — 600 m above the level of
the sea, August — September 1901; i specimen, and N'Kogo,
French Congo, December 1902, i specimen.
Gharinus africanus n. sp.
PI. I, fi.gs. I a — I c.
This species agrees completely with the characters of the
genus Charinus in Kraepelin's analytical key excepting as to
one feature, y\z. that the first tarsal joint is conspicuously
longer than the four others combined.
Cephalothorax in adult specimens considerably broader
than long, with six thin spines at the rounded front margin.
The distance between each ocular tubercle and the lateral
8 studies on Arthropod a. I.
margin nearly or scarcely twice as long as the transverse dia-
meter of the tubercle.
Interior prehensile margin of the basal joint of the antennae
with four teeth, and the most distal tooth bifid, while the ex-
terior margin has no tooth.
Palps about as long as the body. Trochanter with two small
processes on the anterior margin (in fig. la the proximal spine
is overlapped, not visible) ; the robust process on the lower
side with a number of strong setae on the inner and lower sur-
face. Femur in the adults at least a little shorter than the
cephalothorax ; its upper front margin proximally with two
small, conical, setiferous tubercles, more distally three or four
processes, the first moderately long, the others decreasing in
length, and the fourth, if present, quite short; the lower front
margin (fig. i a) with at least three processes decreasing in
length from the first to the third, and the first which originates
near the base, is long; sometimes a small or very small fourth
jjrocess is found. Tibia on the upper margin with four processes
(fig. lb), the second and especially the third very long, strong,
with a setiferous protuberance or rather an offset on the prox-
imal side somewhat from the base; the first process is only
about half as long as the next, but longer than the fourth;
frequently " a setiferous conical protuberance is found before
the first real process; the lower margin (fig. la) on the di.stal
half with two moderately long processes, the proximal shorter
than the distal, and this margin has besides three or four quite
small setiferous tubercles. First tarsal joint has on the upper
margin (fig. i c, u) near tiie middle two processes, the
second considerably to very mucli longer than the first, while
the lower margin has a single moderately long, jjorrected pro-
cess a little before the end. Second tarsal joint (fig. i c) with
two slender processes on the upper margin, the distal from con-
Pedipalpi, Ricinulei, and Opiliones.
siderably longer than to twice as long as the first; the lower
margin without any process.
The three posterior pairs of legs have the metatarsus di-
stinctly longer than the tarsus; first tarsal joint about one-
fourth as long again as the four other joints combined.
The dorsal surface of the cephalothorax in the adult some-
what dark reddish-brown, with the impressions blackish, while
the abdomen is brownish-grey with the muscular impressions
dark and very conspicuous. Antennae, palps, and femora of
the legs somewhat lighter than cephalothorax; legs without
yellowish or Ught rings.
Length of the body of a large specimen 8.4 mm, cephalo-
thorax 3 mm, palp stretched out 8.8 mm (claw included), se-
cond leg (coxa not included) 14.5 mm.
Remarks. — C. ajricamis is allied to C. australianus L.
Koch, but is instantly distinguished in having the first tarsal
joint in the three posterior pairs of legs very conspicuously
longer than the four other joints combined. Furthermore adult
specimens of C. australianus have, according to Kraepelin, a
higher number of processes on both margins of the tibia of the
palps than is found in C. africaniis.
Occurrence. — Taken on three of the Islands in the Gulf
of Guinea: Annobon, St. Thome and Principe. On Annobon
6 specimens were taken in May 1902 in an altitude of 400
— 500 m, and i specimen in April in o — 500 m. On St. Thome
3 specimens were gathered in December 1900 at Agua Ize,
altitude 400 — 700 m, and 11 specimens in September — Octo-
ber 1900 at Visto Alegre, altitude 200—300 m. On Principe
7 specimens were secured in Jan. — March 1901 at Roca In-
fante Don Henrique, altitude 100 — 300 m. — Adult specimens
from St. Thome are a little smaller than those from the two
other islands.
10 studies on Arthropocla. I.
Paracharon n. gen.
Ceplialotliorax not much broader than long, anteriorly
somewhat produced, with a rather short, transverse, anterior
margin. Eyes and ocular tubercles completely- want-
ing (fig. 2 a). First sternum is a light transverse strip more
firmly chitinized than the membrane at its front margin, but
instead of a sternal labium only a tin}- granule with a small
vertical seta is seen at the middle of the sternum. Each of the
two following sterna have a rather slender, subcylindrical
process projecting nearly vertically downward, Ingher than
thick, and with some short, brown setse on the rounded distal
part. — Second abdominal sternite simple, as its posterior
part is not marked off or produced. — Palps considerably
shorter than the bod}-, built as in the Charontidoi; first tarsal
joint (fig. 2 d) with two spiniform processes on each margin
and the distal processes much longer than the proximal; second
tarsal joint with three processes on the upper margin, and the
claw marked off but not movable. Walking legs as in the Cha-
rontidse, excepting that the tibia of fourth pair consists only
of two subjoints.
Remarks. — This most interesting genus differs from
all other genera of the suborder in having no eyes and
no sternal labium. It shows, howe\-er, close relationship
to the Charontidae in all other features, excepting that
the fourth pair of tibia? ha\-e only a .single secondary arti-
culation.
It ma}- be noted that I have looked in vain for sensors-
hairs on the places of the eyes. But the normal long tactile
hairs on the walking legs and the peculiar small, clu])-shaped
sensory hairs on the distal tarsal joints of the first pair of legs
exist, though less numerous, as in the large form Tarcntula
reniformis L. {Phrynichus nigrnnanus C. L. Koch) (see H. J.
Hansen: Organs and Characters in different Orders of Arach-
Pedipalpi, Ricinulei, and Opilioues. II
nids, in Entom. Meddel. Kjobenhavn, Vol. IV, 1893 — 94,
P- 154—156).
Only one species is known.
Paracharon caecus n. sp.
PI. I, figs. '2 a — 2e.
Cephalotliorax (fig. 2 a) only about one-eighth as broad
again as long, considerably vaulted, with the radiating im-
pressions partly deep ; the antero-lateral margin is a little con-
cave, the front margin transverse, rather short, with about
six minute, very short spines.
Palps scarcely twice as long as the cephalothorax. Tro-
chanter with two small processes on the anterior margin (fig. 2 a) ,
while the well developed process on the lower side (fig. 2 b)
has five or six triangular, setiferous teeth on the inner margin.
Femur not fully half as long as the cephalothorax (fig. 2 a) ;
its upper front margin has near the middle two somewhat
small processes; the lower margin has three to five processes,
the first somewhat long (fig. 2 b), the second distinctly or con-
siderably longer than the first, the others small. Tibia has on
the upper margin (fig. 2 c) three well developed processes, the
second process considerabh' longer than the first or the third,
and besides generalh' two small teeth placed respectively before
the first process and between first and second process; the
lower margin (fig. 2 b) has three processes, the second verv'
long and the others rather short, and besides frequently a
minute tooth before the first and another before the second
process. First tarsal joint large and only somewhat shorter
than the tibia ; each margin (figs. 2 b and 2 d) has two pro-
cesses, the distal long or very long and much longer than the
proximal, and besides a distinct or rudimentary' tooth is fre-
quently seen on the lower margin just before the proximal
process, and sometimes a rudimentarv tooth before the distal.
12 Studies on Arthropoda. 1.
process. Second tarsal joint (figs. 2 b and 2 d) has along the
upper margin (u) three processes increasing in length from the
first to the third which is moderately long; the lower margin
has only a single moderately short process.
In second and third pairs of legs the metatarsus is about
as long as the tarsus, and first tarsal joint is somewhat longer
than the four distal joints combined. Fourth pair of legs (fig. 2 e)
have the tibia divided by a single secondary articulation
into two sub joints, the first more than three times as long
as the second; metatarsus somewhat longer than in the
preceding pairs of legs and conspicuously longer than the
tarsus.
Upper surface of cephalothorax in the adult dark yellowish
brown, with the deep portions of the impressions dark brown;
abdomen above light greyish with a somewhat yellowish tint.
Antennae, palps, and femora of the legs nearly as, or a little
lighter than, the cephalothorax; the legs without light rings.
Length of the body of a large specimen y.^ mm, cephalo-
thorax 2.8 mm, palp stretched out (claw included) 5 mm, se-
cond leg (coxa not included) 8.6 mm.
Remarks. — The specimens have been found in nests
of Tennes (genus and species not noted) ; only a single speci-
men has no indication on this topic on the label.
Occurrence. — Portuguese Guinea (near lat. 12° N.) at
two places: Bolama, June — December 1899, i spec; Rio Cas-
sine, Jan. — Febr. 1900, i spec, and April 1900, 15 spec.
B. Sub-order Uropygi.
This sub-order comprises two tribes, Oxopoei and Tarta-
rides, which differ in several important features. No specimen
of the Oxopoei was found among the material, but it contains
a number of specimens of the Tartarides.
Pedipalpi, Ricinulei, and Opilioiies. I3
Trihe Tartarides.
In H. J. Hansen and William Sorensen: The Tartarides.
A Tribe of the Order Pedipalpi (Arkiv for Zoologi utgif. af
Svenska Vet. Akad. Stockholm, Band 2, Nr. 8, 1905) I described
15 species of this most interesting group, mentioned a Califor-
nian species established by Cook but unknown to me, and pointed
that Artacarus liberiensis Cook must be considered a nomen
nudum. Since 1905 Randall Jackson has described (1907) an
interesting form taken in the Botanic Gardens, Kew; in three
small papers (1911) F. H. Gravely established no less than
2 species from Ceylon and 4 from India; K. Kraepelin (191 1)
established a new species from Formosa; Hirst (1913) a species
from the Seychelles; finally H. J. Hansen (1910) a new species
from Kihmandjaro. Thus in all 26 species have been really
described, but of these only 2, viz. Schizomus montanus H. J. H.
and Trithyreus africanus H. J. H., are of African origin. And
it may be added that both these species have been established
on female specimens which certainly or scarcely had not arrived
at sexual maturity, and consequently the knowledge must be
somewhat imperfect. The Fea collection contains adult spec-
imens of both sexes of two new species, and this material is
therefore ver>' valuable, though the forms do not exhibit peculiar
features expanding the general conception of the type.
Trithyreus parvus n. sp.
PI. I, figs. 3 a — 3 k.
Male.
Head with an oblong, rounded, badly limited paler eye-
spot on each side, but without an\- cornea. Cephalic sternum
a little longer than broad. Second thoracic tergite with a nar-
row and whitish median strip of thinner skin.
Palps (figs. 3 a and 3 b) somewhat slender, about two-thirds
as long as the body. Trochanter has the lower front part some-
lA Studies on Arthropoda. I.
what produced, with the terminal margin straight, the comer
angular, and this angle measures 90° — 95°. Femur uncommonly
slender, more than two and a half times as long as deep, with
the lower margin nearly straight though slightly sinuate, but
without any protruding angle towards the base. Patella a little
less than three times as long as deep. Tibia slightly more than
three times as long as deep. Tarsus unusually long, as its upper
margin is as long as the lower margin of the tibia; claw only
one-fourth as long as the upper margin of the tarsus.
First pair of legs (fig. 3 a) slender, somewhat more than
half as long again as the body. Coxae terminate scarcely before
the outer angle of the mandibles (maxillae auct.). Femur a little
longer than tibia. Foot a little shorter than tibia, about nine
and a half times as long as deep (fig. 3 d), deepest near the end
of metatarsus; second joint of the metatarsus almost as long
as the sum of the four proximal joints plus half of the fifth
joint of the tarsus; terminal joint a little longer tlian fourth
and fifth tarsal joints combined, and a little more than half
as long as the whole metatarsus.
Fourth legs somewhat longer than tlie body; femur scarcely
two and one-third times as long as deep (fig. 3f).
Three posterior abdominal segments telescoped and very
considerably thicker (fig. 3 i) than in the other sex ; last seg-
ment without any protuberant part above the insertion of the
flagellum.
Flagellum (figs. 3 h and 3 i) of very moderate size, somewhat
less than twice as long as broad, but almost two and a half
times as long as deep, consequently its thickened part consider-
ably depressed. The stalk rather compressed, seen from above
a little more than one-third as long as the main piece. Seen
from above, the main piece is only one-fourth as long again
as broad, broadest at the middle, with the proximal half of
the lateral margins rather convex, and the distal half to a little
Pedipalpi, Ricinulei, and Opiliones. 15,
from the end conspicuously concave; the end is angular. Seen
from the side (fig. 3 i) the lower margin of the whole flagellum
is shaped as a line somewhat curved or convex at the middle,
while the upper margin is incurved considerably before the end.
The flagellum has several pairs of long or very long spiniform
setae distributed on the sides, at the end and on the lower sur-
face, while the upper side has only two erect shorter setse far
from one another in the median line.
The walking legs, the upper surface of abdomen, and the
posterior part of the dorsal side of cephalothorax are more or
less olive-green with a reddish or light reddish tint ; front part
of the head, antennae and palps reddish; the lower surface of
the body lighter.
Body without flagellum 2.64 mm., palp 1.75 mm., first leg;
4.1 mm., fourth leg 2.9 mm.
Female.
It agrees with the male in many particulars, but differs in
several features.
Palps (fig. 3 c) a little more robust and proportionately shorter
than in the male, being only about half as long as the body.
Trochanter has not the lower distal part produced, and the cor-
ner is a rather obtuse angle measuring about 110°. Femur con-
siderably deeper than in the male, scarcely twice as long as
deep, and the lower margin is angularly bent a little from the
base: the tip of this angle is a Uttle nearer to the proximal
than to the distal end of the upper margin of the joint. Patella
and tibia shghtly thicker than in the male, while the tarsus is
conspicuously shorter than in that sex, and the claw is some-
what more than one-third as long as the upper margin of the
tarsus.
First pair of legs slender, slightly longer than the body.
Coxae terminate a little before the outer angle of the mandibles..
l6 studies on Arthropod a. I.
Femur distinctly longer than the tibia. Foot a little shorter
than tibia, almost ten times as long as deep (fig. 3 e) ; second
joint of metatarsus slightly longer than the four following
joints combined; terminal joint conspicuously more than half
as long as the whole metatarsus.
Fourth legs considerably shorter than the body; fenmr
about twice as long as deep (fig. 3 g) .
Three posterior abdominal segments (fig. 3 k) much more
slender than in the male.
Flagellum (fig. 3 k) a little or considerably shorter than
in the male, nearly four times as long as deep, three-jointed,
but the first articulation is more or less obsolete; the terminal
joint a little more than two-thirds of the whole length.
The largest female which has been taken as type, has the
body 3.3 mm. long, the palp is 1.63 mm., first leg 3.4 mm.,
fourth leg 2.8 mm. Other females, which seem to be
adult, are only about as long as the male, but the relative
length between body, first leg, etc. about as in the large
female.
Colour and other characters not mentioned in this descrip-
tion nearly as in the male.
Remarks. — As usual the palps and the flagellum in botli
sexes afford the best characters. T. parvus is easily distingui-
shed from T. africanus H. J. H. (1905) in having the last tar-
sal joint of first legs considerably shorter in proportion to more
proximal joints, in the shape of the fenmr of the palps, etc.
The differences between T. parvus and the next species are
pointed out below.
Occurrence. — Ten .specimens, among them two adult
males, were collected on the Island of St. Thome at Vista
Alegre, altitude 200 — 300 m., October 9, 1900. An innnature
female was secured at Punta Frailes, Isl. of Fernando Poo,
Oct. 1901.
Pedipalpi, Ricinulei, ami Opiliones. I7
Trithyreus brevicauda n. sp.
PI. I. figs. 4 a — 4fl; PI. TI, fig.s. I a — I g.
Male.
Head without any distinct eye-spot on the sides. Cephahc
sternum much longer than broad. Second thoracic tergite with
a sharp median suture.
Palps (figs. I a and i b) moderately robust, somewhat less
than half as long as the body. Trochanter with the lower
distal part sUghtly produced, the comer acute but the angle
measuring about iio°. Fennir a little less than twice as long
as deep, subtriangular, but the median part of the lower margin
convex without any angle, and its deepest point a little longer
from the proximal than from the distal end of the upper margin.
Patella a Httle less than two and a half times as long as deep ;
tibia slighth^ more than three times as long as deep. Tarsus
not elongate; its upper margin a little more than half as long
as that of the tibia. Claw distinctly less than half as long as
the upper margin of the tarsus.
First pair of legs (fig. i a) moderately robust, somewhat
longer than the body. Coxae terminate somewhat before the
outer angle of the mandibles. Femur somewhat longer than
the tibia. Foot as long as the tibia, between eight and a half
times and nine times as long as deep (fig. 1 e), deepest towards
the end of the metatarsus ; second joint of metatarsus nearly as
long as the sum of the four proximal joints and half of the
fifth joint of the tarsus; terminal joint slightly longer than
fourth and fifth tarsal joints combined, and distinctly more
than half as long as the whole metatarsus.
Fourth legs a little shorter than the body. Fenmr two and
one-third times as long as deep (fig. 4 b).
Three posterior abdominal segments telescoped (fig. 1 g)
and somewhat thicker than in the female; last segment without
any protruding part above the insertion of the flagellum.
1 8 studies on Arthropodn. I.
Flagellum (figs, i f and i g) uncommonly small, a little more
than twice as long as broad, but almost three times as long as
deep, consequently its thickened part considerably depressed.
The stalk only a little deeper than broad, seen from above (fig.
I f) scarcely one-third as long as the main piece, which is oblong-
ovate, not quite half as long again as broad, with the lateral
margins moderately convex and the end very obtuse, rounded.
Seen from the side (fig. i g) the lower margin of the flagellum
has its shorter proximal part feebly conca\'e and the remain-
der somewhat convex; the upper margin has the ])roximal
half somewhat sinuate, the distal somewhat conca\'e and nearly
angularly bent at the middle. Several of the spiniform setae
lost in the single specimen; the upper surface has beyond the
middle a pair of setae and more proximally a seta in the median
line.
Colour nearly as in T. parvus, though a little more
brownish.
Length of the body 3.13 mm., palps 1.4 nun., first leg. ^.^
nun., fourth leg 3.0 mm.
Female.
Similar to the male in most respects; the sexual differences
are less numerous than in most species.
Palps (figs. I d) differ feebly from those in the male. Tro-
chanter has the lower distal corner rounded and not angular,
but the angle measures as in the male about iio^.
First pair of legs (fig. i c) as long as the body. The coxae
terminate distinctly longer from the outer angle of the mandibles
than in the male. Foot slightly longer than tibia, differing
from that in the male in having the terminal joint proportio-
nately a little longer (fig. 4 a), somewhat longer than fifth and
fourth joints combined, and considerably more than half as
long as the whole metatarsus.
Pedipalpi, Ricinulei, and Opiliones. IQ
Fourth legs considerably shorter than the body; femur
(fig. 4 c) a little shorter than in the male, a little more than
twice as long as deep.
Three posterior abdominal segments somewhat less deep
than in the male.
Flagellum (fig. 4 d) even a little longer than in the male,
scarcely five times as long as deep, three-jointed ; third joint
scarcely twice as long as the two proximal joints combined.
Length of the body 3.15 mm., palps 1.40 mm., first leg
5.15 mm., fourth leg 2.77 mm.
Remarks. — T. hrevicauda is closely allied to T. afri-
caiuts H. J. H., which was established (in 1905) on a probably
immature female from Freetown. But the specimen of T. ajri-
canus, which was 2.9 mm. long, thus only a httle smaller than
the adults of T. hrevicauda, differs from these in having the
claw of the palps conspicuously shorter, and besides especially
in the foot which has the terminal joint proportionately much
longer than T. hrevicauda, and though this joint is proportio-
nately longer in immature than in adult specimens, the diffe-
rence between the relative length of this joint in T. africanus
and T. hrevicauda is so large that my adult specimens cannot
belong to T. africanus. It may be added that the foot of T. afri-
canus is nine time as long as deep, thus nearly more slender
than those in T. hrevicauda, but in immature specimens the
foot is less slender than in adults of the same species. — The
small flagellum of the male differs \'ery considerably from that
organ in males of other species hitherto known.
Occurrence. — Bolania in Portuguese Guinea (Kerry
coast), December 11, 1899; 3 adult specimens (i c?, 2 ?).
20 Studies on Arthropoda. I.
ORDER RICINULEI
The main paper on this small but most interesting order is:
H. J. Hansen and W . Sorcnscn: On Two Orders uf Arachnida.
Opiliones, especially the suborder Cyphophthalmi, and Rici-
nulei, namely the famil>- Crj^tostemmatoida^. Cambridge.
At the l^niversity Press. 1904 (4to). — Since its publication
nothing, as far as I know, has been added to our knowledge
of the recent forms. But a curious attempt by Prof. Fr. Dahl
(Berlin) may be briefly mentioned. In 191 1 he published a
small treatise: Die Horhaare (Trichobothrien) und das System
der Spinnentiere (Zool. Anzeiger \'ol. XXXVII, p. 522 — 532).
He ascribes a high systematic value to the exi.stence and distri-
bution or non-existence in the various orders of Arachnida of
that kind of sensor}' hairs which he names "auditory hairs" ;
besides, without an}' real discussion and without pointing out
any feature hitherto overlooked in the orders Pedipalpi, Pal-
pigradi, Ricinulei, Opiliones, and Acari, he refers the Palpi-
gradi to the Pedipalpi, the Ricinulei to the Opiliones, and the
suborder Cyphophthalmi from the Opiliones to the Acari. That
such classification is only of the retrograde kind is rather evi-
dent; it is scarcely necessary to prove its futility Ijy detailed
enumerations of structural features and a lengthy discussion
of their relative value in the orders and suborders in question.
In a paper published in igi/'^). I have dealt with the so-called
"auditory hairs" in Arachnida and in the two other classes of
terrestrial Arthropoda. — On the palaeozoic forms of the order
Ricinulei important contributions have been published by
') H. J. Hansen. On the Trichobothria ("auditory hairs") in Arachnida,
•Myriopoda, and Insecta, with a summary of the external sen.sory organs
in Arachnida (Entomologisk Tidskrift utg. av I-.ntoinol iMirenineen i
Stockhohii. Arg. 38, xgiy, p. 240 — 259.
Pedipalpi, Ricinulei. and Opiliones. 21
R. I. Pocock (1911) and especially by A. Petninkevitch (1913).
It is remarkable that as to the palaeozoic genus Pnlyochera
Scudder, which seems to be rather allied to recent forms, the
last-named author mentions only one generic character, viz.
that "tarsus of second leg fused with metatarsus, forming one
joint", but this character is important, as in the recent forms
the second pair of legs has in the adult a separate, well devel-
oped metatarsus, and the tarsus live- jointed.
The material collected by Fea comprises two species, one
among them new, while the other species is (ryptostemma
crassipalpe Hans. & Sor, which was established on immature
specimens, but Fea has secured adult specimens of both sexes.
Of the new form a large material is to hand, which enables me
to add a little on a couple of points to the description in Hansen
& Sorensen's work, and besides to show that a kind of metamor-
phosis exists in this order, as I have two specimens of a larval
stage with only three pairs of walking legs.
In the paper mentioned the spiracles and the tracheae in
the immature Cryptostemma was described (p. 131 — 132).
I have dissected an adult male of C. Fece n. sp. and found a
similar structure, so that only one single particular may be men-
tioned. On the crescent-shaped spiracles we wrote: "The walls,
particularly near the opening, are furnished with short, extre-
mely thick, slighth' branching hairs . . . which almost have
the character of processes, and at least in part are free of each
other". In the adult I have found that both the convex and the
concave margin of the crescent-shaped spiracle have a very
close layer of processes which are very oblong, and each with
a number of moderately short, acute spines in ever}' direction.
Each layer has a certain thickness, as it is formed by a few rows
of processes. The processes are on both margins shorter towards
both ends of the spiracle, and when the processes of the two layers
reach each other with their ends, they constitute with their
22 Studies on Arthropoda. I.
lateral thorns a kind af sieve for the air. The processes are
light brownish.
In 1904 we showed that in the female of the large form Ciyp-
tostemma Afzelii Thor. the sternites of first and second abdo-
minal segments are freely movable, crescent-shaped, with their
concave margins turning against each other, and they surround
together the genital aperture; both sternites are only visible,
when the abdomen is bent much upwards. In C. Fcce n. sp.
I find the same structure, but the sternites are a little less robust.
In this species — and probably in all other forms of the order
— the genital aperture is in the male much smaller than in the
female; the sternite of second segment is very thin and semi-
circular or in reality curved so nmch, that it occupies about
three-fifths of a circle; the sternite of first segment is produced
downwards as a freely protruding, triangular plate about as
long as broad and with the end subacute. The same plate is
also found in the adult male of C . crassipalpc. An internal co-
pulator}^ organ is, as might be expected, completely wanting,
l)ut according to my dissection of a single male, the inner sexual
organs and the alimentar}- canal can scarcely be made out
with certainty without fresh material or at least the sacrifice
of several well preserved specimens of both sexes.
The Larva. — The body is about 2.3 mm. long, second
leg 3.3 mm. In general aspect the body of the larva is in the
main similar to half-grown specimens, differing in being compa-
ratively a little broader, with the grooves on cephalothorax
partly feebly developed, partly wanting, and without grooves
on the cucullus, while the tergites of the abdomen and the gra-
nulation are nearly as in postlarval younger stages. But the
larva has only three pairs of walking legs, as the
fourth pair is completely wanting (pi. Ill, fig. i g).
That it is the fourth pair which is wanting is seen from
the fact, that the coxtc of first, second, and third pairs
Pedipalpi, Ricinulei, and Opiliones. 23
are immovabl}- united as in the adults, while in the
adults the coxae of fourth pair are movable. Furthermore
the larva differs from postlarv'al stages in the tarsi of second
and third pairs of legs. The tarsi of third pair (pi. Ill, fig. i i)
have only two joints, the second not fully twice as long as the
first, but otherwise not showing any peculiarity worth mentio-
ning. But the tarsi of second pair (pi. Ill, fig. i h) are interesting.
Each of them has only two joints, both very large, somewhat
compressed and very deep, much deeper than the metatarsus;
the proximal joint is more than one-tliird as long as the metatar-
sus, only a little longer and deeper than the second, which has
the claws and even the normal subdistal sensory hair (s.) nor-
mally developed. — The interesting fact that the Ricinulei
thus possess a larval stage with only three pairs of walking legs
removes the order further from all other orders of Arachnida
except the Acari, but in nearly all other structural features
hitherto known the Ricinulei have no affinity to the Acari.
Cryptostemma crassipalpe Hans. & Sor.
PI. II, figs. 2 a — 2 h.
This species was established on two immature specimens,
one among them not far from full-grown, with the full number
of joints in the tarsi, but the animal was light-coloured, and the
tergites of the three large abdominal segments were rather
removed from each other. The material collected by Fea com-
prises two immature specimens and five adult animals of both
sexes. It may be convenient to begin with the young specimens.
The largest of the immature specimens is somewhat smaller
than the type, as its body is only 4.2 mm. long, while the type
was 4.8 mm. It agrees well with the description and figures
quoted, excepting that the femoral part of the palps is only
half as thick as long, while in the type it was distinctly more
than half as thick as long, but this difference is in other forms
2d. Studies on Arthropoda. I.
due to age. When viewed obliqueh- there ma>- 1)e observed a
faint vestige of the sublateral impression on the cnculhis, wliile
in the type this feature was not perceived.
Adult specimens. — Body and legs brown or dark l^rown
and on some places reddish ; the granules which are extremely
numerous, especially on the body, are in immature specimens
purple and therefore very conspicuous in contradistinction to
the yellowish skin, but in the adults they are not distinctly
marked off by colour from the skin ; v. hen the adult animal is
flried it changes its aspect, as the exceedingly numerous scales
are \'ery light, being somewhat slate-whitish with a yellowish
tint, and consequently the animal looks rather clayey, darkest
on the median ])ortion of tlie ventral surface where the clotliing
is less dense.
The cephalothorax has the same outline and dorsal grooves
as the subadult type, but it differs in a curious feature. A me-
dian area, nearly triangular with the sides convex, is raised
l)etween the end of the median groove and the posterior margin
as a moderately large, rounded j^rotuberance or rather low
tubercle badly marked off, which in the male is directed mainh'
upwards, in the female upwards and considerably backwards,
so that in the latter sex the cephalothorax seen from above
(fig. 2 a) has the median part of its posterior margin very con-
spicuously ccmvex.
Tlie cucullus (fig. 2 b) seems to be slightly broader in pro-
])ortion to length than in young specimens, and a sublateral
oblong impression is distinct, but real grooves are not developed.
The palps (fig. 2 c) have the femoral part a little or conspi-
cuously more than half as thick as long. The tibial i)art is ador-
ned with numerous granules on more than its distal two-thirds,
and these granules are oblong and rather coarse on the most
distal third. - (As usual in adults the thick connecting skin bet-
ween tlie large abdominal tergites has nearly disappeared).
Pedipalpi, Ricinulei, and Opiliones. 25
Sexual differences are found in the above-named protu-
berance on the cephalothorax and in the three anterior pairs
of legs. First legs are scarcely or distinctly thicker in the male
(fig. 2 d), than in the female (fig. 2 e), but at least the shape of
the metatarsus is rather different in the two sexes ; in the female
the metatarsus is moderately slender, with the same thickness
in its whole length, and its lower, inner margin is feebly convex;
in the male the metatarsus is thicker, increases a little in
thickness from the base to a little from the end, and the distal
two-thirds of its inner margin is much more convex than in
the female. Second legs are somewhat varying, as the}- may
be similar in both sexes or a little stouter in the male.
The copulatory organs (fig. 2 g) on third pair of legs on the
whole similar to those in C. W ester mannii Guer. and C. Sjo-
stedtii Hans. & Sor. ; of course the movable process of first tar-
sal joint has a shape of its own and affords as usual excellent
specific characters. It may be mention(^d that the metatarsus
from in front (fig. 2 g, 6) is somewhat more than twice as long-
as thick; its movable process has the most distal slender part
curved ver\' considerably backwards. First tarsal joint {d)
is uncommonly long, being, seen from below, only somewhat
shorter than second and very much longer than the third,
which is somewhat shorter than the fourth. The second tarsal
joint {e) has the distal triangular process {e^) of the front wall
rather small, while the lamina cyathiformis {e"), is high, and
consequently the upper end of its wall is more than twice
as far from the distal lower end of the joint than is the case
with the tip of the process from the front wall. The movable
process {d^ — d~) of first joint has the distal segment about twice
as long as the proximal; the distal segment seen from the
outer side (fig. 2 h) is rather narrow, the proximal process from
its front margin is situated considerably before the middle^
and is somewhat short, oblong-triangular, and very acute;
26 Studies on Arthropoda. I.
the distal part of second segment is produced into three pro-
cesses, but the two drawings (figs. 2 g and 2 h) may convey a
sufficient idea of the curious shape of the whole part.
In the male the body is 4.4 mm. long, second leg 7 mm.;
in the female the body is 4.7 mm. long, second leg 6.9 mm.
Remarks. — C. crassipalpe is easily separated from the
other species hitherto known of the genus in having the bod\-
and most of the legs covered with very broad scales, which are
not much longer than Inroad or almost as broad as long.
Occurrence. — Island of Fernando Poo, at two places:
Musola, altitude 400—500 m., Januar}- 1902, 2 males, 3 females,
I immature specimen; Basile, altitude 400 — 600 m., August —
September 1901, i young specimen.
Distribution. The specimens described by Hansen and
Sorensen were from Kameroon, the part of the continent oppo-
site to the Isl. of Fernando Poo.
Cryptostemma Feae n. sp.
ri. IT, figs. 3 a — 3c; PI. Ill, figs. I a — i i.
A. Adult Female.
Closely allied to C. Ajzclii Thorell as described by Hansen
and Sorensen, so that it ma\ be advisable to lay special stress
on the differences.
Cephalothorax slightly longer than broad. Its surface is
adorned with numerous moderately large granules conspi-
cuously lower than high and of a special structure, as their
outline is circular, the upper surface ver\' moderately arched,
marked off from the sides by a sharp outline, very finely stria-
ted, and besides ver\^ dark coloured, brownish l>lack, while
the; sides of the granules are greyish; between the granules a
number of feebly clavate hairs somewhat or considerably lon-
ger than the height of the granules; the whole adornment of
the surface differs ^rom that in C. Afzelii in having the granules
Pedipalpi, Ricinulei, and Opilioiies. 7,y
conspicuously less closely set and the hairs longer. The lateral
margin of the cephalothorax is considerably less concave be-
fore the submedian angle than in C. Afzelii, and the angle
mentioned is less protruding. The median groove is well devel-
oped, reaches to or nearly to the front margin, is posteriorly deep,
and at its end is seen a short transverse groove. The marginal
groove — along the anterior half of each lateral margin — is well
developed; as in C. Afzelii two grooves forming a right angle
with one another are seen on the area between the median
groove and the submedian angle of the lateral margin.
Cucullus (fig. 3 a) as long as broad at the base, and beyond
the middle half as broad again as at the base ; the submarginal
grooves moderately developed. The surface is adorned with
numerous granules, which are smaller but proportionately
bigher than on the cephalothorax and otherwise of the same struc-
ture; betw^een them are found a number of minute granules
and besides hairs; these hairs are considerably longer than the
height of the larger granules, subclavate, and towards the front
(lower) margin of the cucullus the hairs are longer, cylindrical,
at the margin still longer and acute. — The cucullus differs
from that in C. Afzelii in having the granules less closely set.
Abdomen above with granules and hairs quite as cephalo-
thorax ; from the middle to the posterior end the granules are
gradually a little smaller and more numerous. On the ven-
tral side the granules are very numerous and quite small and
low, but somewhat larger towards the posterior end.
The antennae (fig. 3 b) as in C. Afzelii with five teeth on the
distal posterior margin of first joint, but they differ in being
longer than broad; the inner margin of second joint is more ar-
med than in C. Afzelii, as it possesses a row of about eight
rounded teeth.
The palps (fig. i a) ha\-e the trochanterical part on the front
side set with numerous small granules, wdiich are much larger
ZS Stvidies on Arthropoda. I.
near the lower margin. The femoral part a little more than
twice as long as thick, especially on the anterior side with a
good number of small granules and numerous hairs, most of
them moderately short, but no impressed points are found.
The tibial part is slightly or a little thicker somewhat from the
base than at the middle, but towards the end it is feebly or very
feebly thickened, conspicuously less so than in (\ Afzclii; its
anterior side, excepting a proximal part, is granulated, and
the granules are nmch larger on the distal third, largest and
l)esides oblong towards the end; on the proximal major part
the hairs are as on the preceding joints, while several of the di-
stal hairs are long and simple.
The legs have their joints, excepting the tarsi, adorned
with numerous granules of the same quality as those on
the surface of cephalothorax, but they are on the whole pro-
portionatel}' a little higher, less broad, with the terminal dark,
striated area nmch smaller (fig. ; c) ; the hairs as on cephalo-
thorax ; the adornment differs from that in C. Afzclii in having the
granules less dense and the hairs somewhat longer. All femora
with a conspicuous longitudinal furrow above ). Tibia of second
pair with a distinct, that of fourth pair with a less distinct
longitudinal dorsal furrow, which is wanting on first and third
tibia; first tibia twice as long as thick. Fourtli joint of second
tarsus half as long again as the fifth, which is distinctly longer
than third joint.
Colour dark reddish brown, with the limbs a little lighter,
more reddish. Some ten specimens probably captured a short
time after the last mould, have the body lighter reddish brown
and the limbs more or less ferrugineous.
Length of tlie body 6.4 mm., of second leg 8.5 mm.
^) Here 1 inaj- correct a inis.soript in Hanson and Soren.sen'.s paper. In the
description itself of C. Afzclii the femora are correctly .stated to have
;i longitudinal dorsal furrow, but in the diagnosis is said: "femora supra
non sulcata" and the word "non" must be cancelled.
Pedii)al[)i, Ricinulei. ami (^piliones. 2Q
Male.
Similar to the females in most features, but differs strongh*
in thickness and shape of the two anterior pairs of legs. First
legs (fig. I b) are on the whole stouter than in the female (fig.
I c) ; tibia and metatarsus are nmch thicker and differently
shaped. Tibia only half as long again as thick (in the female
twice as long as thick), thickened below but without any pro-
cess; metatarsus widened below, with the inferior margin con-
spicuously more convex than in the female. — Second legs
(fig. I b) extremely altered ; femur always enormously thickened
upwards and downwards, but yet showing considerable indi-
vidual variation; in the specimen figured the femur is a little
less than twice as long as deep at the middle (in the female
(fig. I c) about four times as long as deep) , but in one specimen
it is scarcely two-thirds as long again as deep; the femur has
therefore both the upper and the lower margin very convex
but it is much compressed; besides the granules on the major
part of the anterior and the posterior side are feeblj^ developed,
and in some specimens the dorsal longitudinal furrow has
disappeared, while it is distinct in other specimens. Tibia on
the lower side near the base produced into a long and thick,
obtuse, a little curved process directed downwards and forwards,
and granulated as the remainder of the joint. Metatarsus has
frequently a short portion near the middle of the lower margin
distinctly produced as an oblong, low protuberance, but in
other specimens this expansion is very feeble.
The copulatory organ, excepting its movable process on
first tarsal joint, agrees so closely with that of C. Karschii
Hans. & Sor. described and figured in 1904, that it may be
omitted here. As usual the movable i)rocess mentioned has a
shape of its own, affording specific characters. Its second seg-
ment is more than twice as long as the first (fig. i e) ; seen from
the outer side (fig. i f) its major distal part is lamellar and rather
^O studies on Arthropoda. !.
I
broad ; the proximal process at its front margin protrudes before
the middle of the segment, is long, broad at the base and tapers
towards the broadly obtuse end. The most distal part of the
segment has a moderately long, cur\^ed, distally slender process
and besides a pair of short, triangular processes; the compli-
cated shape may be judged from the two figures.
Length of the l)ody 6.6 mm., of second leg lo mm.
Immature Specimens.
Specimens not far from full-grown differ as usual from the
adult female in the colour ; the cephalothorax is yellowish ferru-
gineous, the abdomen greyish and the legs browni.sh yellow;
furthermore, in the palps the femoral part is more slender, the
tibial part has the subbasal portion conspicuously thicker
than the middle, and it increases scarcely in thickness from
the middle to the end.
A younger specimen, which has only four joints in the tarsi
of fourth pair but the full number in the other pairs, is 4.1 mm.
long, with second leg 5.6 mm.; it has the palps more slender
than in older specimens, and the sublateral impressions on the
cucullus are scarcely discernible.
One of the smallest specimens (the real larvit excepted)
is 3.1 mm. long with second leg 4.2 mm. It has only four joints
in second tarsus, three joints in third, and two joints in fourth
tarsus. Cephalothorax has the median groove well developed
excepting towards the anterior margin, but some of the other
grooves are partly or wholly indi-stinct, and the cucullus has no
sublateral impressions. The animal is more yellowish than older
specimens.
The lar\a \\\\\\ three i)airs of legs has been described abov-e
(p. 22).
Remarks. — As already mentioned C. Fca is uUied to
C. Afzclii, but it is much smaller, the granules on body and
Pedipalpi, Ricinulei, and Opiliones. 3^
limbs are more scattered, and the distal portion of the tibial
part of the palp is less thickened. As the male C. Afzelii is
unknown, it is at present impossible to point the secondary
sexual differences between the males of the two species.
Occurrence. — Portuguese Guinea (near lat. 12° N.), at
two places: Bolama, June — December 1899, many specimens;
Rio Cassine, January — April iqoo, numerous specimens.
ORDER OPILIONES
This order comprises three sub-orders, viz. Palpatores,
Laniatores, and Cyphophthalmi. The collection contains a
rich material of the Laniatores, but with the consent of Dr.
Gestro it has been handed over to a colleague. The small but
interesting material of the two other sub-orders is dealt with
on the following pages.
Sub-Order O. Palpatores.
It is an interesting and curious fact that Mr. Fea, who was a
most excellent collector, has secured only two specimens du-
ring his voyages in West Africa; animals of this sub-order
must consequently be very scarce in the countries investigated.
Both animals are fortunately adult males; they belong to two
different genera, and both belong to the family Phalangioidse.
A few years ago Dr. C. Fr. Roewer published the two first
l)arts of his monograph of the Palpatores in: Abhandlungen
aus dem Gebiete der Naturwiss. heraug. vom Naturwiss. Ver-
ein in Hamburg. The second part of this work has the title:
Revision der Opiliones Palpatores (^ Op. Plagiostethi) , II
Teil; Familie der Phalangiidse (1. c. Vol. XX, I, 1912) ; it deals
J2 Studies on Artliropoda. I.
with three of the six sub-families into which he divided the
family. On p. lo he separates the sub-family Phalangiina*
from the iive others in having no horizontally protruding pro-
cess on the lower side of first joint of the antennse (he named
these appendages mandibles), while such a process is constantly
found in all the other sub-families. According to this definition
my two genera belong to his Phalangiina?. But it has been
more difficult to refer them to any of the numerous genera
accepted or established b}' Dr. Roewer; one of them I refer to
an old genus, but I find it necessary to establish a new genus
for the reception of the other.
Dacnopilio insularis n. s]).
ri. Ill, figs. 2a -Ml.
Male.
Body oblong, with the posterior margin, seen from above,
somewhat flatly rounded; the skin coriaceous and ratlier flexible.
Surface of cephalothorax with a considerable number of con-
spicuous, triangular, acute denticles distributed in the following
way : a transverse group of about sixteen such denticles occupies
the anterior half of the area in front of the ocular protuberance,
and some among these spines are placed on the front margin ;
obliquely outside and in front of each antero-lateral angle of
the ocular protuberance a single denticle is found, while each
more lateral part of the surface has eight or nine denticles.
The supra-antennal area has below a pair of very distinct den-
ticles, and between this pair and the upper margin rudiments
of a second pair. The two posterior thoracic segments are well
marked off, and each has a transverse row of similar teeth.
The ocular protuberance is middle-sized, longer than liigli,
without an>' median furrow, but armed with se\'en rather
low teeth distributed in two rows (fig. 2 b) ; the protuberance
is scarcely as long as its distance from the front margin.
Pedipalpi, Riciimlei, and Opiliones. 33
The five anterior abdominal tergites each with a transverse
band of small denticles: on the fifth tergite this band is narrow,
consisting of a row and closeh* in front of this some few dentic-
les; on the other tergites the band is broader and the denticles
are placed more irregularly. On the sixth tergite denticles
are ver^' feebly developed, while the two following tergites
are smooth.
The antennae are considerably elongated and thickened,
stretched out nearly as long as the body. First joint is directed
forwards and considerably upwards, twice as long as thick,
somewhat cur^'ed, with most of the upper margin rather con-
vex (fig. 2 c) , while the lower margin has its long middle part
concave and is convex towards both ends. The upper surface
of the joint has a number of denticles a little smaller than those
on the cephalothorax, while the major posterior part of the
lower surface has a lower number of somewhat longer teeth;
the sides are nearly smooth. Second joint twice as long as,
but not thicker than, the first, and measured to the tip somewhat
more than three times as long as third joint; seen from the side
the upper margin of second joint is mainly directed forwards
and conspicuously concave which is due to a pronounced trans-
verse impression; the joint from the upper margin to the inser-
tion of third joint is a little fusiform, and the upper part of
its front surface has a moderate number of somewhat small
denticles.
Palps somewhat longer than the bod}', moderately strong,
%vith the tarsus slender. Trochanter obliquely triangular with
some teeth on the upper side. Femur a little longer than the
tarsus, increasing in thickness from base to near the end, suban-
gular, with longitudinal rows of small, acute denticles. Patella
without apophysis, but with some quite minute denticles on
the upper surface. Tibia without apophysis, a little curved,
on the lower side with one denticle or two minute denticles
3
]4 studies on Arthropoda. I.
somewhat from the base, and a minute denticle at the terminal
margin. Tarsal claw simple.
Legs of middle length. P'irst coxae with a considerably num-
ber of granules, each with a short, black seta; the other coxae
with the granules and setae more feebl}^ developed. First pair
of legs with femur, patella and tibia considerably thicker than
in third or fourth pair, and much thicker than in second pair.
Femora of first pair only a little shorter than the body, conspi-
cuoush' claA'ate (lig. 2 d) and somewhat cur\'ed, with longitu-
dinal rows of well developed, triangular denticles and a number
of scattered denticles, but without any process at the end. Se-
cond femora considerably longer than the body; the three po-
sterior pairs of femora with rows of denticles distinctlj' smaller
than those on first pair. Patellae and tibiae of all legs with the
denticles conspicuously smaller than those on the respective
femora and partly rudimentar\- ; tibiae more or less subangular.
Colour of the body yellowish-grey, with some dark spots
above; palps light yellow, but their femora, excepting at the
end, the proximal part of tibiae and the end of the tarsi dark.
Legs in the main as the palps, with the distal part of the femora
and patellae brownish, while the subdistal i:)art of the tibiae
is only slightly darker than the proximal jiart.
Length of the body 5.6 mm., first legs (without coxae) 20
mm., second legs 34.5 mm.
Remarks. — This new species is more related to Dacno-
pilio Roewer than to any other genus. Roewer has described
two species, which differ much from one another in armature
and probably also in size of the mandibles in the male, and the
new species seems in some features to l)e intermediate between
the two other African forms.
Occurrence. — The single specimen, an adult male, was
taken in February iqo2 in 1300 — 1400 m. above the level of
the sea at Moka on tlie Island of Fernando Poo.
^ Pedipalpi, Riciniilei, and Opiliones. 35
Megistobunus n. gen.
Allied to Megahumis, but differs in several features.
Body very small, with the dorsal skin coriaceus and rather
hard, excepting on the three posterior abdominal segments.
Cephalothorax highly vaulted (fig. 3 a), even somewhat coni-
cally raised above, and last segment distinct; no frontal median
spine: supra-antennal area without denticles. Abdomen has
the tergites of the five anterior segments fused nearly as a
.shield, but each segment has a spiniform process or denticle
in the median line.
Ocular protuberance extremely large, constricted at the base,
and adorned with a few pairs of extremely long processes;
e3'es proportionately small.
Antennse somewhat small, normal and simple in the male;
first joint without ventral process.
Palps (fig. 3 c and 3 d) longer than the body, moderately
slender. Femur with longitudinal rows of triangular denticles,
but without longer processes. Patella with a half dorsal, half
interior apophysis which is long and somewhat slender. Tibia
on the inner side produced into a quite short but distinct apo
physis. Tarsus nearly as long as the femur; claw simple.
lyCgs extremeh^ long. First coxae scabrous below, as they
have a number of irregularly scattered granules while the
other pairs are less scabrous, and no pair possesses any regular
row of denticles at the anterior or posterior margin. Femora
similar in shape and thickness, without any secondary articu-
lation, but ^^•ith rows of small denticles; no elongate spines
at the end of femora or patellae.
Remarks. — The genus is established on a single adult male.
The animal is in general a.spect rather similar to a very long-
legged Liobunum, a genus from which it is very remote in im-
portant features. It is related to Megahunus, but differs from
the forms of this genus in the following features: the dorsal
3*
36 studies on Arthropoda. I.
cuticle of the cephalothorax and of the major part of abdomen
is rather hard ; the front margin of the head without any strong
median process; the five coalesced abdominal tergites each
with a median spine; the femora of the palps without processes
and only with normal denticles below ; the legs extremely long,
and all denticles quite small ).
Megistobunus longipes n. sp.
PI. Ill, tigs. 3a — 3d.
Male.
Cephalothorax highly vaulted ; its penultimate segment mo-
derat.el}^ its last segment well, marked off. The front margin
with a few small denticles. Above the openings of the stink-
glands is at each side a longitudinal row of three oblong-trian-
gular processes, and a smaller denticle is seen near the base
of the ocular protuberance; between this protuberance and the
frontal margin several minute denticles are scattered. The
first thoracic segment has at the front margin a transverse row
of three pairs of conspicuous teeth and a couple of denticles
at the lateral margin; second segment has a transverse row
with some few denticles.
The ocular protuberance extremely large, with three pairs
of conical, slender and very diverging processes (fig. 3 b) ; the
third pair arc exceedingly long, a little longer than first pair,
and about twice as long as second pair. The protuberance,
^) When I looked over Dr. Roewer's descriptions of the genus M e g a b u n u s
and its three species, I found his work very far from satisfactory. In the
diagnosis of the genus he says: "Palpen kraftig", but in the description
of M. diadem a: "Palpen klein und schwach", and at the two other
species respectively: "Palpen klein" and: "Palpen kiirz". In the diag-
nosis of the genus he says: "Beine lang and diinn", in the description
of M. diadema: "Beine nicht sehr lang; diinn", of M. rhinoceros:
"Beine kiirz", and of M. (irouvellei: "Beine diinn, wenig lang". That
generic characters as those quoted on Meg a bun us are .sheer nonsense
can scarcelv be denied.
Pedipalpi, Ricinulei, and Opiliones. 37
excepting a lateral portion around each eye, is set with
numerous denticles, among which those in a narrow belt
below the eyes are somewhat large, and the denticles diminish
nmch in size downwards and disappear near the base of
the protuberance; the processes are armed with conspicuous
denticles.
The abdominal shield has a median row of five spiniform
processes or teeth ; the process on second segment is larger than
that on the first, and the latter is larger than the third, while
those on fourth and fifth segment are mere denticles; first and
second segment each besides with a transverse row of two pairs
of conspicuous denticles, while on the three other segments
corresponding denticles are small or wanting. The free abdo-
minal tergites and the ventral surface of the abdomen nearly
smooth .
Palps not inconsiderably longer than the body. Trochanter
distally with a few granules above and below. Femur a little
cur\'ed and slightly thickened towards the end, with rows of
denticles on the lower side and granules on the upper surface.
Patella with two marginal rows of granules above ; the apophy-
sis slightly longer than the patella itself (fig. 3 c and 3 d) and
somewhat shorter than the tibia, moderately slender, but with
the subdistal part slightly thickened and everywhere clothed
with short hairs. Tibia proximally with very incomplete rows
of granules; the terminal inner apophysis (fig. 3 d) is short,
shorter than broad, hair>\
Legs extremely long, ver>' slender. Coxae of first pair with
a moderate number of irregularis^ scattered, setiferous granules,
while the other pairs are less scabrous. Femora subsimilar,
excepting that second pair are distinctly more slender than
the first, and all with rows of small denticles; patellae with very
few denticles, while the denticles on the tibiae are very small
and partly rudimentary.
38 Studies on Arthropoda. I.
Colour of the body, antennse, palps and coxae 3'ellowish;
the upper side of abdomen, trochanter and femur of the palps
with a brownish tint, the patellar apophysis and the apex of
the palps brown, the distal part of the antennal fingers black;
ocular protuberance and its processes black excepting the
constricted base. Legs dark yellowish brown, patella; dark
brown, trochanter and base of femora brownish black.
Length of the body 3.8 mm., first legs 28 mm., second legs
64.5 mm., fourth legs 44.5 mm.
Remarks. — In general aspect rather similar to Liohunitm ;
second pair of legs seventeen times as long as the body.
Occurrence. The single specimen was captured in Au-
gust — September 1901 in an altitude of 400 — 500 m. at Basile
on the Island of Fernando Poo.
Sub-order O. Gyphophthalmi.
The main work on this sub-order is H. J. Hansen and W.
Sorensen: On two Orders of Arachnida. Cambridge 1904. It
contains descriptions of two genera from Africa, each with a
single species, viz. Ogovia grossa H. J. H. & W. S. from Ogove
in sequatorial France, and Purcelliu illnstrans H. J. H. & W. S.
from Cape. The material to hand comprises a new species of
Ogovia and another form, for the reception of which a new
genus must be established.
Ogovia Hans. & Sor.
This characteristic genus hitherto comprised a single spe-
cies, 0. grossa, established on an adult female, and the male
was unknown. The new species, though easily separated from
0. grossa, agrees excellently with every cliaracter found in
the generic description excepting as to two particulars, viz.
that the produced median frontal plate is so large that it cannot
be called "brevior", and that the inner marginal keel of first
Pedipalpi, Ricinulei, and Opiliones. 39
pair of coxse is proportionately somewhat shorter, being scar-
cely half as long again as the distance between its end and the
tip of coxa. As both sexes of the new species are to hand, it
may be added to the generic description that the sexes differ
from one another not only in the two usual points, viz. the shape
and position of the genital aperture and the male process on
the upper side of fourth tarsus, but besides the abdomen has
in the male behind the genital aperture a process directed much
backwards, and the median anterior part of the ventral abdo-
minal surface is excavated.
Ogovia nasuta n. sp.
PI. Ill, figs. 4a — 4c; pi. IV, figs- I a — if.
Male and Female.
Body thick, scarcely three-fourths as long again as broad,
considerably broader than deep, with the median part of the
dorsal surface of abdomen and of the hind part of cephalothorax
rather flatly convex.
Cephalothorax anteriorly produced into a proportionately
large, triangular and much vaulted plate (figs, i a and i b)
which is somewhat broader than long with the end subacute,
the lateral margins a little convex, and the surface densely
and finely granulated; this plate overlaps the major part of
first joint of the antennulse. The lateral surface between the
lamina mentioned and the "conus foetidus" — the process with
the aperture of the odoriferous gland at the end — is somewhat
hollowed, so that the anterior median part of the cephalothorax
is shaped about as a ver\" broad, rounded keel; the posterior
transverse furrow is much arcuate, posteriorly at the middle
flatly concave and a little or considerabh' nearer to the furrow-
limiting the abdomen than the length of the first abdominal
tergite at the median line. The surface is ver^'- densely and
finely granulated and besides, excepting anteriorly on the sides.
^.0 Studies ou Arthropoda. I.
adorned with a number of much larger, scabrous and badly
defined granules or rather quite small, irregular tubercles.
The "coni foetidi" are subtriangular (fig. i a), broader than
long, directed outwards and somewhat forwards; their anterior
margin is, seen from above, somewhat convex to a little from
the protruding terminal part, but seen from in front this shape
is seen to be due to the fact that each conus has its front subter-
minal part considerably excavated at the anterior end of the
two labial plates limiting the terminal orifice.
Abdomen above with granules as on the major part of ce-
phalothorax. The seven anterior tergites divided by a shar]>
furrow in the median line. On the \'entral side (fig. i b) the
first furrow is curved forwards inside the spiracle and reaches
the margin of fourth coxa. The anal operculum is somewhat
vaulted, and seen partly from behind distinctly broader than
long. The whole ventral surface is densely and moderately
finely granulated, excepting the hollowed median part in the
male mentioned later on.
Antennae (fig. 4 a) nearly as in 0. grossa. I'irst joint has the
dorsal transverse rounded keel very conspicuous, and the upper
and most of the outer side of the free part of the joint is dis-
tinctly granulated. The hand of the chela is somewhat less
than three times as long as broad, smooth on the anterior side,
and not fully twice as long as the movable finger.
Stomotheca conspicuously more than half as long again as
broad at the distal end (figs, i c and i d).
Palps (fig. 4 b) about as long as the antenna^ measured from
the proximal margin of the transverse dorsal keel, in the main
as in O. grossa, yet differing in having the trochanter a little more
slender and femur more oblique with l^otli tlie upper and the
lower margin more convex.
T^egs ver>' short and thick, considerably shorter than in
0. grossa. I^ower surface of first pair of coxae not lower than
Pedipalpi, Ricinulei, and Opiliones, 41
on second pair. Femora of first pair (fig. 4 c) conspicuously
cur\'ed upwards with the lower margin rather concave excepting
towards the base, of second pair feebly curv^ed, while the two
other pairs are straight (fig. i e). Tibiae somewhat longer and
deeper than the patellae, in the anterior pairs about half as long
again as deep, in fourth pair proportionately a little longer.
Tarsi of first pair (fig. 4 c) slightly less deep than the tibiae,
and the "solea" occupies little less than half of the lower mar-
gin of the tarsus.
The upper side of the body with numerous extremely short,
thick, fusiform or rather clavate hairs which increase a httle
in number posteriorly, so that they are closer on the posterior
abdominal tergites than on the cephalothorax ; the ventral
surface has a number of normal hairs which are longer and thicker
on the coxae than on the abdomen, where they are short
and \'ery thin. The legs, excepting their tarsi, have a number
of \-er\^ short, fusiform hairs on the upper surface and normal
hairs on the lower side of the joints, while the tarsi have only
normal hairs which on the lower side are longer than on the other
joints — excepting of course the solea of first pair which is
densely clothed with verj^ short and thin hairs. The palps
have the three distal joints well haired, while the hairs on their
femoral part are shorter and less numerous, and the trochanter
has only some hairs on the most distal part; the first joint of
the antennae has a \'er>' moderate number of hairs.
Sexual differences well developed. In the female the tar-
sus of fourth pair of legs normal, shaped as the preceding pair;
in the male the fourth tarsus (fig. i e) increases nearly gradu-
ally conspicuously in height from rather near the base to beyond
the middle, and it is above at the middle produced into a
moderately large, nearly regularly conical, .slighth' curved
process which is somewhat longer than deep at the base
and directed l)ackwards and considerably upwards; this
^.2 Studies on Arthropoda. I.
process is scarcely di\-ided into a proximal and a much shorter
distal part.
In the male the genital aperture (tig. i c) is nearly twice as
broad as long, with the anterior margin considerably curved,
the posterior margin feebly concave; the genital arculi [m)
posteriorly rather narrow, anteriorly considerably widened
inwards, at the median line about as long as the aperture,
and with the anterior, the inner, and the posterior margin of
their front part distinctly raised. No genital operculum is
marked off, but a little behind the genital aperture projects
a large, broad, oblong, subacute process (p) directed down-
wards and mainly backwards; this process is somewhat depres-
sed and even slightly hollowed on the proximal part of its lower
side; at the sides and behind this process the ventral surface
of the abdomen is considerably excavated, and the excavation,
which is oblong, occupies more than half of the surface between
the base of the process and the front (lower) margin of the
anal operculum. — In the female (fig. i d) the genital aperture
is still shorter than in the male; the genital arculi are not mar-
ked off from the coxa? and each terminates in a subacute angle.
The genital operculum is not marked off posteriorly, in front
it is very narrow with the end cut off transversely, and it is
deeply impressed just behind that end; the surface of abdomen
has no process and no excavation as in the male.
Colour dark. Body and first joint of the antennae from dark
reddish-brown to blackish brown; the distal joints of the an-
tennae and the legs more or less dark reddish-brown, with the
tarsi frequently a little lighter; palps brownish yellow, with
tlie distal joints lighter.
In the male figured the body is 3.45 mm long and 2 mm
broad, cephalothorax 1.6 mm long, first leg 2.5 mm, fourth
leg 2.6 mm. The single female is 3.52 mm long and 2.07 mm
broad.
Pedipalpi, Riciuulei, and Opiliones. 43
Remarks. — 0. nasiita is distinguished from the female
of 0. grossa b}' a number of features, and some among them
may be pointed out. The frontal plate overlapping the antennae
is much longer and broader than in 0. grossa; the granulation
on the upper side of the body is \-ery different, the legs con-
siderably shorter in proportion to the body, and the solea of
the first tarsus is conspicuously longer in proportion to the-
length of the whole lower margin of the tarsus.
A curious feature may be mentioned here. On the two figu-
res of the legs (figs. 4 c and i e) are seen some rings (x), viz.
femur, tibia and tarsus each with two rings (the distal ring of
fourth femur placed on its upper margin), patella and meta-
tarsus each with a single ring; each ring signifies a circular
area which is well marked off, considerably vaulted and very
smooth and shining. Similar areas are also found both above
and below on the body; on fig. i b an area (x) is seen on each
■coxa, and a pair on most of the abdominal sternites. Similar
vaulted,' shining areas has also been obser\'ed in 0. grossa, but
they have not been found in any other genus of the suborder.
One is inclined to think that these areas, which as to outer
shape and aspect are somewhat similar to small eyes, may
be organs of some quite unknown significance.
Immature Specimen. — The animal (fig. i f), measuring
2.3 mm in length, is proportionately broader than the adults.
The body is yellowish brown; the articulating skin between
the five posterior abdominal sternites constitutes darker trans-
verse bands; the legs are light yellowish. Fig. i f as compared
with fig. I b shows several differences due to age : lobe of second
pair of coxae feebly developed, the surroundings of the future
genital aperture ver>- dift"erent from the structure in the adult,
with broad membrane around the arculi (;«) (first abdominal
sternite), finally the bands of articulating skin between the
abdominal sternites.
\A Studies on Arthropoda. I.
Occurrence. — The material, consisting of 3 adult males,
I adult female and an immature specimen, was taken at Musola,
Island of P'ernando Poo, January 1902, in an altitude of 400 —
500 m.
Parogovia n. gen.
Cephalothorax anteriorly produced into a triangular plate
(fig. 2 a), which covers at least the inner part of the transverse
keel on first joint of the antennae. A median keel on cephalo-
thorax is not developed.
Eighth and ninth abdominal sternites completeh^ fused,
and besides fused with the ninth tergite so that not even a
vestige of any furrow between these plates is seen (fig. 2 b) .
No eyes.
"Coni foetidi" moderately long, seen from above nearly
obUquely triangular, directed outwards and feebly upwards,
and about half as long from the lower margin of the cephalo-
thorax as the length of the basal diameter of the cone. The
end of each cone has a ver}' oblong and ^'ery convex, smooth
and shining area or piece, which looks almost as a single mode-
rately thick lobe.
First joint of the antenna" (fig. 2 e) not reaching to the end
of the fenmr of the jjalps, considerably compressed, on the lower
side raised as a large, rounded tubercle, and above with the
proximal transverse keel well developed. The teeth on the mov-
able finger subsimilar in shape, moderately high, rounded;
on the fixed finger two kinds of teeth alternate (fig. 2 g), half
of them being larger than on the movable finger, moderately
high and rounded, while each interval between two such teeth
is occupied with an extremely low but somewhat broad tooth,
with the free margin a httle convex.
The palps (fig. 2 h) have the trochanter proximally slender,
distally much thickened with some granules, somewliat shorter
Pedipalpi, Ricinulei, and Opiliones. 45
than the femur which is slender and scarcely compressed; the
tarsal joint scarcely as long as the tibial.
First pair of coxse (figs. 2 c and 2 d) anteriorly produced
into a triangular process; the distance between the front end
of that process and the angle terminating the marginal keel
of the stomotheca is only somewhat shorter than the length
of the last-named keel. Stomotheca with the middle parts of
its limiting keels nearly parallel, and towards the end it is a
httle widened, only somewhat narrower at the front end —
between the angles — than the length of the marginal keels.
The thin-skinned part of each maxillar\' lobe (fig. 2 c, h) is
divided into two portions distant from one another; the basal
portion is normal, while the distal portion constitutes a freeh'
protruding, oblong, rounded lappet.
First pair of coxae considerably broader than those of second
or third pair, and much narrower than fourth pair (fig. 2 b).
Metatarsi conspicuously more than half as long as the tarsi.
Solea of first pair of tarsi (fig. 2 i) occupies considerably more
than half of the length of the lower margin of the tarsus, and
is rather well defined from the proximal part of the lower side.
Tarsi of first and second pairs without any longitudinal
dorsal furrow.
Claws simple, without saw-teeth; those of fourth pair of
legs (fig. 2 k) much longer than first pair (fig. 2i),
Sexual differences only found in the genital aperture with
the arculi, and in the tarsi of fourth pair.
Remarks. — The genus Parogovia, which most decidedly
belongs to the subfamily Stylocellini H. J. H. & W. S., agrees
with Ogovia and differs from Stylocellus especially in five cha-
racters, viz. that the cephalothorax is anteriorly produced
into a triangular plate, that it has no eyes, that eighth and
ninth abdominal sternites are completely fused with one an-
other and with the ninth tergite, that first coxae are produced
^.6 studies on Arthropoda. J.
into a triangular process, and that the two anterior pairs of
tarsi have no dorsal furrow. It agrees with Styloccllns and
differs from Ogovia in having the claws on fourth pair of tarsi
much longer than first pair, and in some features in the palps,
as their femoral part is not expanded and conspicuously longer
than the trochanter, their tibial part longer than the tarsus.
It differs from both genera in having the membranous part
of the maxillary lobe of first coxa; developed in a peculiar way,
in the aberrant terminal part of the coni foetidi, in having
no trace of dorsal keel on the cephalothorax, finally in the
antennulae, as the first joint has a single large tubercle on the
lower side, and the fixed finger has two kinds of teeth.
The single species known is in general aspect somewhat similar
to Siro, though it decidedl}^ belongs to the other subfamily.
Parogovia sironoides n. sp.
PI. IV. fi?;.s. 2 a — 2l.
Bod}- (fig. 2 a) • moderately thick, more than three-fourths
as long again as broad, nmch broader tlian deep.
Ce])halothorax almost as long as the abdomen (fig. 2 a) ,
anteriorly without real lateral excavations and without an>-
median keel; the front lamina of moderate size, triangular,
broader than long, subacute. The posterior transverse furrow
is much arcuate, \'ery feebly developed excepting at the middle,
where it is more distinct and flatly curved, and here its distance
from the furrow limiting the abdomen is three or four times
shorter than the length of first abdominal segment. The sur-
face of cephalothorax is rather densely granulated; the gra-
nules are well developed, not confluent; the lower side of the
coxae more finely granulated.
Coni foetidi nearly as long as broad; the end is rounded
and shows, seen from above, an oblong and oblique, smooth,
shining area.
Pedipalpi, Ricinulei, and Opiliones. 47"
Abdomen with the tergites undivided in the median line
and densel}^ granulated; the granules, which on first tergite
are nearly as on cephalothorax, decrease gradually in size
posteriorly, so that they are distinctly smaller and besides
more dense on the posterior tergites. On the ventral side the
first furrow is moderately curved (fig. 2 b) and terminates
without being produced forwards inside the spiracle; the anal
operculum is somewhat vaulted, and seen partly from behind
broader than long; the whole ventral surface is densely and
finely granulated.
Antennaf rather long. First joint seen in situ from above
(fig. 2 a) four times as long as broad at the base, and here scar-
cely as broad as the conus foetidus; it is granulated above
and on the more proximal part of the lower side. The hand
of the chela is a little more than five times as long as broad
(fig. 2 f ) , smooth on the anterior side, and more than three
times as long as the movable finger.
Palps (fig. 2 h) about as long as the externally \-isible part
of the antennae. Femur considerably longer than the trochanter,
about four and a half times as long as deep, with several gra-
nules on the lower margin. The tarsal part slightly shorter
and a little thicker than the tibia.
Legs (figs. 2 i and 2 k) moderately robust; first and fourth
pairs a little shorter than the body. Surface of first pair of
coxa- not lower than that of second pair. Femora of first pair
with the distal half distinctly curved, so that the lower margin
is conspicuously concave (fig. 2 i) ; the other femora nearly
straight. Tibia somewhat longer, but not deeper, than the
patella, about twice as long as deep. Tarsi of first pair
(fig. 2 i) a Httle deeper than the tibia, with the lower
margin rather angular somewhat before the middle, and
tlie solea occupies about three-fifths of the lower margin of
the joint.
^.8 Studies on Arthropoda I.
The upper side of the body moderately haired; all hairs
\-ery thin and most of them very short, cylindrical, not acute;
the lower surface of abdomen has but few hairs, while on the
coxx the hairs are more numerous and moderately long. The
legs have a good number of hairs (figs, zi and 2 k), most of
them normal, acute, but on the proximal joints and especially
on the femora many of the hairs are shorter and not acute.
The palps hairy excepting the major proximal ])art of their
trochanter (fig. 2 h) .
Sexual differences only moderateh' conspicuous. In the
female the tarsus of fourth pair is shaped as third pair; in the
male the fourth tarsus is near the base on the upper side (fig. 2 k)
produced into a process as long as the depth of the tarsus,
rather slender, somewhat tapering from the base to beyond
the middle, with the short distal part (fig. 2 1, ^) marked off
and oblique-triangular, acute; the process is directed some-
what upwards and much backwards and is distinctly cur\'ed ;
the upper surface of the tarsus below the proximal half of the
process is, seen from the side, somewhat concave. — In the
male the genital aperture (fig. 2 c) is nearly circular ; a genital
operculum is not marked off posteriorly, but its front margin
is almost semicircularly concave; the arculi are somewhat
narrow, almost three times as long as broad at the base, and
not nmcli decreasing in breadth from the base forwards. In
the female (fig. 2 d) the genital aperture is a little smaller than
in the male and differs somewhat in shape; the genital oper-
culum {r), which is very short, is marked off by a transverse
impression, and has its front margin straight, and tliis margin
is much shorter than the breadth of the aperture; the arculi
are moderately broad and at the l)ase considerably broader
than in the male (m), with the inner margin regularly concave.
Colour. — The body is dark reddish brown, with the
coxa: and the anterior part of the cephalothorax still darker,
Pedipalpi, Ricinulei, and Opiliones. ^.Q
blackish; legs and antenme lighter reddish brown; palps yel-
low.
The single male is 2.46 mm long and 1.47 mm broad, ce-
phalothorax 1.21 mm long, antennae from the base of the trans-
verse keel 1.58 mm long, palp 1.58 mm, first leg 2.3 mm, fourth
leg 2.3 mm long. The female is about of the same size; its body
is 2.48 mm long and 1.41 mm broad.
Remarks. — Rather similar to species of the genus Siro,
but proportionateh' broader, with the legs a little shorter and
conspicuously thicker, and besides differing in the shape of
the front margin of the cephalothorax and in several important
features (shape of stomotheca, and of both pairs of maxillary
lobes, hairs on second antennal joint, etc.).
Occurrence. — The two specimens were captured in the
Island of Fernando Poo; the male at Punta Frailes in Oct. —
Nov. 1901, the female at Basile in Aug. — Sept. 1901 in an
altitude of 400 — 600 m.
Explanation of the Plates.
Plate I.
Fig. I. Charinus africanus n. sp.
Fig. I a. Left palp, from the lower, outer side; X 8.
— lb. Left tibia, from the upper side; X 8.
— I c. Left tarsus, from the outer side; X 8. — n. upper
margin.
Fig. 2. Paracharon caecns n. gen., n. sp.
Fig. 2 a. Cephalothorax with antennae and left palp, from
above; x 8.
— 2 b. I,eft palp, from the lower outer side; X 13.
4
^O studies on Arthropoda. I.
Fig. 2 c. Left tibia, from the upper side; x 13.
— 2d. Left tarsus, from the outer side; X 13. — tt. upper
margin.
— 2 e. Distal joints of left fourth leg, from above; X ^^/g.
Fig. 3. Trithyreus parvus n. sp.
Fig. 3 a. Left palp and first leg of the male, from the outer
side; x 20.
— 3 b. Left palp of the male, from the outer side; X 35.
— 3 c. Left palp af the female, from the outer side; X 35.
— 3d. Left first foot of the male, from the side; x 47.
— 3 e. Left first foot of the female, from the side; X 47.
— 3 f . Left fourth leg of the male, from the side ; x 20.
— 3 g. Left fourth leg of the female, from the side ; x 20.
— 3 h. The three posterior abdominal segments with fiagel-
lum of a male, from above; X 60.
— 3 i. The same segments with fiagellum of a male, from
the side; x 60.
— 3 k. Posterior abdominal segments with flagellum of a
female, from the side; x 60.
Fig. 4. Trithyreus brevicauda n. sp. (continued).
Fig. 4 a. Foot of first left leg of the female, from the side ; X 46.
— 4 b. Left fourth leg of the male, from the side; X 20.
— 4 c. Major part of left fourth leg of the female, from the
side; x 20.
— 4 d. Posterior abdominal segment witli fiagellum of a
female, from the side; X 62.
Plate IL
Fig. I. Trithyreus brevicauda n. sp. (continued).
Fig. I a. Left palp and first leg of the male, from tlie outer
side; x 20.
Pedipalpi, Riciiiulei, and Opiliones. 5 1
Fig. I b. Left palp of the male, from the outer side; X 43.
— I c. Left palp and first leg of a female, from the outer
side; x 20.
— id. Left palp of a female, from the outer side;
X 43-
— I e. Foot of first leg of the male, from the outer side;
X 46.
— if. Posterior abdominal segments with flagellum of a
male, from above; X 62.
— I g. Posterior abdominal segments with flagellum of a
male, from the side; X 62.
Fig. 2. Cryptostemma crassipalpe Hans. & Sor. *
Fig. 2 a. Cephalothorax of an adult female, from above; X 12.
— 2 b. Cucullus of an adult female, from in front; X 16.
— 2 c. Left mandibular palp of an adult female, from in
front; X 22.
— 2d. The two anterior right legs of the adult male, from
above; x 9. — Hairs omitted.
— 2 e. The two anterior right legs of the adult female, from
above; x 9. — Hairs omitted.
— 2 f. Major distal part of first right leg of the female, from
above; X 21.
— 2 g. Distal part of third left leg of an adult male, from
in front; X 25. — a. terminal portion of the tibia;
b. metatarsus; c. its movable process; d. first tarsal
joint; d^. first joint of its movable process; d'^. se-
cond joint of the same process; e. second tarsal joint;
e^. front margin of its distal lower wall of its
'lamina cyathiformis' ; e-. posterior high wall of
the 'lamina cyatluformis' ; /. third tarsal joint.
— 2 h. Tarsal movable process of the organ shown in fig. 2g,
essentially from below; X 58.
52 studies on Arthropod a. I.
Fig. 3. Cryptostemma FecB n. sp.
Fig. 3 a. Cucullus of a male, from in front; X 15.
— 3 b. Left antenna, from behind (from below) ; x 23.
— 3 c. Portion of the front side of the right first femur of
a female; X 65.
Plate III.
Fig. I. Cryptostemma Fece n. sp. (continued).
Fig. I a. Left mandibular palp of an adult male, from in front ;
X 20.
— lb. First and second right leg of an adult male, from
above; X ^^/g.
— =- I c. First and second right leg of an adult female, from
above; x ^^/2. — Granules and hairs omitted.
— id. Major part of first right leg of the same adult female,
from above; X 15.
— I e. Tarsal movable process of the copulatory organ in
third left leg of an adult male, from in front; X 42.
— if. Distal half of the same mo\-able process, from the
outer side; X 47.
— I g. Body with left palp and the more proximal joints
of all three pairs of legs of a larva, from below; X 15.
— I h. Metatarsus and tarsus of second right leg of a larva,
from above; x 21. — s. sensory seta.
— 1 i. Metatarsus and tarsus of third leg of a larva, from
above; x 21.
Fig. 2. Dacnopilio insidaris n. sj).
Fig. 2 a. Body with left antenna and palp of a male, from
the side; X "/a-
— 2 b. Ocular protuberance of the male, from the side; X 24.
— 2 c. Left antenna of the male, from the outer side;
-^ /2-
Pedipalpi. Riciniilei, and Opiliones. 53
Fig. 2 d. Femur of first right leg of the same male, from in
front; X ^'/a-
Fig. 3. Megistohumis longipes n. gen., n. sp.
Fig. 3 a. Body with left antenna, palp, and the proximal
parts of the legs of an adult male, from the side;
X scarcel}^ 8.
— 3 b. Ocular protuberance of the same male, from the
side; x 13.
— 3 c. Left palp of the same male, from the outer side;
X 13.
— 3d. Patella, tibia and proximal part of tarsus of the same
palp, from above; X 16.
Fig. 4. Ogovia nasuta n. sp.
Fig. 4 a. Left antenna of a male, from the outer side; X 24.
— 4 b. Left mandible with palp of a male, from the outer
side; X 24.
— 4 c. First left leg of a male, from the outer side; X 23.
— X. vaulted, smooth and shining circular areas.
Plate IV.
Fig. I. Ogovia nasuta n. sp. (continued).
Fig. I a. Cephalothorax and the two anterior abdominal seg-
ments of a male, from above; x 16. The plate from
the front end covers the major part of first joint of the
antennae; of the palps only trochanter and femur,
of the three following pairs of legs the protruding
ends of the coxae and the proximal part of the
trochanter are drawn; of fourth legs only the end
of the coxae is rendered.
— lb. Body with coxse and trochanteres of all walking legs
of a male, from below; X 14. Antennae and man-
<4 studies on Arthropoda. I.
dibles with palps removed; granulation and hairs
omitted. — x. vaulted, smooth and shining circular
areas.
Fig. I c. Middle portion of the anterior half of the body of
the same male, from below; X 23. — /. angle limit-
ing the stomotheca in front; //. soft portion of the
maxillary lobe of lirst coxa; m. genital arculi; p.
process originating a little behind the genital aper-
ture.
— id. Middle anterior portion of the body of a female ;
from below; X 26.
— I e. Left fourth leg of a male, from the outer side; X 23.
— X. vaulted, smooth and shining circular areas.
— if. Ventral side of an immature specimen; x 15. — m.
genital arculi.
Fig. 2. Parogovia sironoides n. gen., n. sp.
Fig. 2 a. Body with the proximal joints of the appendages
of a male, from above; x 10.
— 2b. Body of the same specimen, from below; x 16. —
Granulation and hairs omitted.
— 2 c. Middle portion of the anterior half of the body of
the same male, from below; x 32. — /. angle limit-
ing the stomotheca in front; h. soft part of the
maxillan.' lobe of first coxa divided into two portions
somewhat removed from one another; m. genital
arculi.
— 2d. Middle portion of the anterior half of the body of
a female, from below; X 32. — r. genital operculum.
— 2 e. Left antenna of a male, from the outer side; X 32.
— 2 f . Second and third joints of the same antenna, obliquely
from the upper and outer side; X 36.
— 2 g. Distal portion of the same antenna; X lOtS.
Pedipalpi, Ricinulei, and Opiliones. 55
Fig. 2 h. I/cft palp of a male, from the outer side; X 32.
— 2 i. First left leg of a male, from the outer side ; x 27.
— 2 k. Fourth left leg of a male, from the outer side; X 27.
— 2 1. Upper part of the tarsus of the same fourth leg more
highl^^ magnified. — s. proximal, and f. terminal
part of the dorsal process.
ON STRIDULATION
IN CRUSTACEA DECAPODA
I. Introductory Remarks.
It is a well-known fact that stridulating organs exist in a
number of species belonging to genera of very different families
of Crustacea Decapoda; most of our knowledge on this topic
down to the year 1899 has been put together by Ortmann in
Bronn: Klassen und Ordnungen des Thierreichs, Bd. V, II.
Abth., Crust. 2, p. 1245. Structural features interpreted as
stridulating organs have been discovered in three species of
PencBOpsis (de Man, 191 1) of the family Penseidae; in several
species of some genera of the Palinuridse (Ortmann, 1. c.) ; in
Thalassina anomala Herbst (Pearse, 191 1) of the family Thalas-
sinida?; in Coenobita ritgosa H. M.-Edw. (Hilgendorf, 1869) of
the family Coenobitidse ; in Clibanarius strigimanus White (Hen-
derson, 1888) of the family Paguridse, and in a number of crabs.
Among the tribe Oxj'stomata such organs are known only in
the species of the genus Matida (Hilgendorf, 1869; Ortmann,
I.e.); in the tribe Oxyrrhyncha they are unknown ; in the old
tribe Cyclometopa they exist in Pscudozius Edwardsii Barr.
(Barrois, 1888) of the family Xanthidae, in Ovalipes bipustulatus
H. M.-Edw. (Wood-Mason, 1878) of the family Portunidse, and
in a few African species of the genus Potamon (Caiman, 1908)
of the family Potamonidse. In the tribe Catometopa organs are
found in all species excepting one of the genus Ocypoda (various
authors), in some species of MacrophtJmlmiis, in Helice and
Metaplax (Hilgendorf, de Man, Ortmann), all l)elonging to the
StricUilation in Crustacea Decapoda. 1. ^'J
family Ocypodidae; finally in some species of Sesarma and Hete-
rograpsus (Hilgendorf, de Man, Ortmann) of the family Grapsidae.
In most cases it is eas}' to recognize a stridulating organ.
Excepting in the genus Potamon and perhaps in Thalassina
(see later on) it consists always of a very regular row of granules
or small tubercles or a file-like series of ridges, playing the role
of a fiddle, while the role of the bow is performed b}^ a ridge
or a small, regular row of granules or very short ridges, or by a
sharjD margin. In some cases, as in Ocypoda, the fiddle is moved
to and fro against the ridge-shaped bow; in other cases, f. inst.
in Penceopsis, the sharp margin acting as bow is moved forwards
and backwards against a ridged area. The structure in Potamon
is completely different: a patch of modified spines on the coxa
of each of the two anterior pairs of thoracic legs is moved
against ver>' modified spines on thickened lobes from the lower
margin of the carapace (Caiman, Ann. Mag. Nat. Hist., ser. 8„
vol. I, 1908, p. 469); the structure in Thalassina is unknown to
me. — The sound has been heard in living animals of at least
two species of Palinurus (several observ^ers), some species of
Ocypoda (Hilgendorf, Ortmann, Anderson, Alcock), Thalassina
anomala (Pearse)^), and MattUa (Ortmann). But even if living
animals have not been obser\'ed, the organ is easily interpreted
when both the fiddle and the bow are well developed, or, as is
the case in Penceopsis, the fiddle is so characteristic that no
doubt remains. But in some cases, f. inst. in Coenobita mgosa,.
the interpretation of the structures in question is less certain,
as either the fiddle or the bow is not developed in such a way,
that it is possible to decide with absolute certainty whether the
^) Pearse's treatise scarcely exists in Copenhagen. But according to Cai-
man's "record" the animal stridulates, and as I have been unable to dis-
cover the organ in question it may be supposed that it is either aber-
rant in structure or perhaps to be found in some unexpected or hidden
place, consequently that Pearse who studied the habits of the animal,
heard the stridulation.
58 studies on Arthropoda. 1.
parts are used by the living animals as a stridulating
organ.
Many years ago I discovered casually a highly developed
stridulating organ in a species of Ovalipcs (family Portunidse),
and afterwards a fine organ in the genus Acanthocarpus , belong-
ing to the family Calappidse in the tribe Oxystomata. The aim of
the present small treatise is not only to describe these new organs,
but to mention the structure in forms of the genus Ocypoda, to
consider the curious occurrence of organs both in terrestrial
forms, in amphibious Decapoda and in real marine species,
two among them inhabiting even moderately deep water,
finally from comparison with other classes of animals to point
out analogies and the need of further biological observ^ations
of living Decapods.
II. Organs in the genera Ovalipes and Acanthocarpus.
I. Ovalipes {Platyofiichus) ocellatus Herbst. — On the lower
side of each half of the carapace and considerably from the
antero-lateral margin is seen a long, narrow, slightly raised area,
which is parallel with the direction of that margin and con-
sequently arcuate; it begins somewhat from third maxillipeds
and reaches to outside the insertion of the cheliped. This area
has a large number of rather coarse, transverse ridges completely
similar to each other in breadth and extremely regularly arranged,
radiating in the direction of the postero-exterior angle of the
coxa of the cheliped. The area is broadest near the middle and
tapers towards both ends and especially towards the anterior
end; consequently the ridges towards this end are gradually
shorter, and those near the end only oblong, small tubercles.
The part acting as bow is found on the merus of the chelipeds,
the upper side of which has proximalh* in front an oblong area
with ver>' regular oblique ridges — in a large female to hand
■8 ridges — and these terminate as slight protul)erances on the
Stridulation in Crustacea Decapoda. I. 59
front margin. When the chehpeds are moved forwards and
backwards a moderatel}' strong sound is produced.
(More than fort^^ years ago Wood-Mason pointed out a
special feature in another species of the genus Ovalipes {Platyo-
nichus), viz. 0. bipustulatus M.-'Edw., and interpreted it as a
stridulating organ. The lower surface of both chelse have a good
number of transverse, serrated ridges, but these are not fully
as regular as usual in a stridulating organ, and I have been un-
able to point out with certainty any part which can act as bow ;
in this case observation of living animals are necessary for
settling the question.)
2. Acanthocarpus Alexandri Stimps. — Both chelae are
similar; each is large, ver}' high, with the inner side somewhat
flat ; on this smooth surface is seen a somewhat curved, vertical,
distinctly raised area somewhat before the insertion of the
movable finger. The area reaches about to the upper margin of
the chela and occupies scarcely three-fourths of its height; its
upper half is somewhat broad, but it tapers rapidly above and
slowly from the middle downwards; the area is adorned with a
high number of very fine and very closely set ridges which are
ver\' obhque on the long median line of the area, and the ridges
are equally close in its whole length. On the lower side of the
orbit and further outwards somewhat below and a little behind
the front margin of the carapace runs an oblique, thick keel,
which is broadest at its middle, narrower towards both ends
and especially outwards ; each keel has 8 or 9 transverse, rounded,
rather thick ridges arranged v^ry regularly, and each interval
is about twice as broad as one of the ridges. When the chela is
moved forwards-upwards and in the opposite direction below
the front part of the carapace, it is rubbed against the ridged
keel described, and produces a rather high sound. — This
species has been taken in West Indies and somewhat more
northwards in depths from 71 to 150 fath. ; one of the
*<fcr«^-V-
/:st,
6o Stiuli-s oil Arthropoda. I.
specimens in the Copenhagen Museum is from near 200
fathoms.
Another species of the same genus is A . bispi)iosus A. M.-lvdw.^
which is described and figured by A. Milne-Edwards and Bouvier
in Memoirs Mus. Comp. Zool. vol. XXVII, no. i, 1902, p. 127;
the specimen was taken in 140 fathoms. Fig. 6 on pi. XXV in
that work represents the inner side of a chela and shows a striated
vertical area not mentioned in the text; this area agrees much
with that found in A. Alexandfi, and accordingly A. hisfinosiis
has a stridulating organ completely as developed as in the other
species.
III. Organs and their use in the genus Ocypoda.
Though the organs found in various species are well known
and even afford excellent specific characters, it is necessar\' for
the following considerations to mention two main types. At
least 14 species of this genus are accepted as \'alid, and a
stridulating organ is found in all excepting a single form. In
this genus the part acting as fiddle is always found in both
sexes on the inner side of the large chela, and that area is rubbed
against a ridge on the lower side of the ischium of the same leg.
In the American O. quadrata F. a robust, subvertical keel is
found somewhat before the fingers, and this keel has a rather
low number of coarse and regularly but not closel}' set granules;
0. platytarsis H. M.-Kdw. from India shows a rather similar
structure. In the Asiatic O. macroccra H. M.-Edw. the keel is
somewhat low, flattened above, with the lower half of its surface
moderately broad, the upper half tapering to the end. Near
the upper end this area has rather coarse ridges moderately
distant from each other; from tlic upper end downwards to
beyond the middle the ridges become gradually finer and more
closely set, and on the lower third they are very fine, and the
impressions between them extremely narrow. In the connnon
Stridulation iu Crustacea Decapoda. I. 6l
Indo-Australian 0. ceratophthalma Pall, the area differs some-
what from that in 0. macroccra ; the area tapers upwards from
a little below the middle, and nearly these three-fifths have
somewhat coarse ridges moderatel}- remote from each other,
while further below the ridges are suddenly ver\' fine, all
equally fine and close together. The area can therefore
be compared with a fiddle bearing two chords;
when its major upper part is moved against the
ridge on ischium the tone produced is deep; when
only its lower part is used the tone is very much
higher. — 0. macroccra can even produce three tones in using
respectively the upper, the middle or the lower part of the area.
On these musical possibilities see later on.
The species of the genus Ocypoda are not marine, but un-
fortunately our knowledge of their biology, especially of their
musical faculties, is imperfect. The best account of a species
is written by Alcock in "Administration Report of the marine
Survey of India for the official year 1891 — 92"; he observed
0. macrocera, and the part of his account (p. 16) necessary for
my purpose shall be reprinted here. "They are gregarious, and
though at times they ma}- be seen marching (migrating?) in
battalions across the sand, the}' usually live in "warrens" at and
above high- water mark, where they excavate tortuous burrows
.... and when alarmed flying each one to its burrow". "The
sounds can be heard, and their effect seen, by forcing one crab,
which we will call the intruder, into the burrow of another,
which we will call the rightful owner. The intruder shows the
strongest reluctance to enter, and will take all the risks of open
flight, rather than do so, and, when forced in, he keeps as near
the mouth of the borrow as possible. When the rightful owner
discovers the intruder he utters a few broken tones of remon-
strance, on hearing which the intruder, if permitted, will at
once leave the burrow. If the intruder be prevented from making
62 Studies on Arthropoda. I.
his escape, the low and broken tones of the rightful owner
gradually rise in loudness and shrillness and frequency until
they become a continuous low-pitched whirr, or high-pitched
growl, the burrow acting as a resonator". In a paper published
in 1900 the same author says: "One almost certain use of the
stridulating-organ is to give warning to intending trespassers,
of its own species".
On 0. ceratophthalma Anderson wrote (Journ. Asiatic Soc.
Beng. vol. LXIII, 1894, p. 138) : "A loud croaking noise .... At
first I imagined it must be caused by frogs, so perfectly did it
resemble the croaking of these animals .... it proceeded from
the burrows of the Ocypoda crab which here fringed the beach
at high-water mark. The burrows are frequently, in coral sand,
very wide at their mouth (6 to 8 ins.) and then taper gradually
downwards, so that they act as excellent resonators. The cause
of the stridulation of the crabs was by no means apparent, the
animals were all lying hidden in their burrows, and several
were croaking at the same time, as if in concert". — Ortmann
visited a place inhabited b}' the same species; he says (1. c.)
that all specimens were in their burrows, and the sound produced
was "a deep bass-tone".
It is easily seen that the curious structure of the fiddle in
0. macrocera and O. ceratophthalma is not explained by the
obser\'ations quoted.
IV. On Stridulation.
Among the above-named stridulating Decapoda the species
belonging to the family Palinurida? and the genera Pcnceopsis
and Acanthocarpus are purely marine animals. Ocypoda is ter-
restrial. Ovalipes ocellatus is amphibious, "not unfrequently taken
at the surface of the sea", and "perfectly at home among the
loose sands at low-water mark, and also abundant on sandy
bottoms off shore" ; "when living at low- water mark on the sand
Stridulation in Crustacea Decapoda. 63
beaches it generally buries itself up to its eyes" (Stebbing, 1893,
from Verrill and Smith) ; Matuta seems to live under rather
similar conditions. The other forms, possessing either decidedly
stridulating organs or features interpreted as such are either
terrestrial [Coenobita rugosa) or amphibious or inhabiting
shallow water at the shore.
Stridulating organs of types built according to the same
principles as in terrestrial or amphibious Crustacea are known
in many Insects and in some Aranese, but it is interesting that
the organs in really marine Decapoda are in principle similar
to those in terrestrial forms. {Potamon and Thalassina are left
out of consideration). The first thing to be noted is that the
organs in Decapoda exist in both sexes; scarcely any species
has been obser\'ed, in which only the male possesses an organ
absent in the female; only in Penceopsis there seems to be some
insignificant sexual difference in the size of the stridulating
area (De Man, 1911).
With good reason Caiman writes (1909) : "In the case of
purely aquatic species, the function of these organs is less easy
to understand". But analogies can be pointed out. A good
number of fishes of very different families are known to produce
sounds ; in many forms the sound is produced by the air-bladder
specially adapted for that purpose, in others by the first strong
ray in the pectoral fins, or the anterior rays in the first dorsal
fin, or the first ray in the ventral fins, or by tlie praeoperculum.
( Readers taking interest in this matter may be referred to the
excellent work by Dr. William Sorensen: Om Lydorganer hos
Fiske. 1884. Sorensen describes and explains the instruments,
but says nothing on their biological use) . A more close analogy
is Corixa, a genus of Hemiptera, of which several species
inhabit fresh water in Europe, and they stridulate ver>^
well; Pelohiiis Hennanni of the family Dytiscidai may also
be noted.
64 Studies on Arthropod a. I.
Stridulating organs built according to the same principle
as in Penceopsis, Acanthocarpus, Palinuridcp, etc. are known in
males of European Aranese as Asagam and Steatoda and in nu-
merous Insects, thus in both sexes of Necrophoridae, in most
Cerambycidae, in the genus Crioccris (fam. Chrysomelidse) , in
several genera of lyamellicornia and in the larvae of at least most
types of that big family (the Lucanidae included), in some other
Coleoptera, in the Reduviidae (Hemiptera), etc. (The organs in
Cicadidae, lyocustidae etc. are omitted here) . In all the terrestrial
Arthropoda enumerated we find an .area, or two areas, with
regularly arranged and generally fine to extremely fine, trans-
verse ridges, and a sharp margin, a row of minute tubercles,
or the end of rostrum acts as bow. We generally know little
and frequently nothing on the biological role of the organ in
most of these Insects, but it must be emphasized that in every
form known to me the ridges on a stridulating are sim-
ilar as to thickness and distance; consequently one
might suppose that only a single tone could be produced, and
that modulation must be rather limited. But that is in reality
not always the case; for the best proof of the opposite, and the
most interesting obser\^ation on the use of stridulating organs
of the normal structure we are indebted to J. C. Scliiodte (Naturh.
Tidsskrift, 3. Raekke, B. VII, 1870, p. 188). Schiodte experi-
mented with specimens of Nccrophorus, especially A^ vespillo,
and writes: "When listening to a flower-pot in which several
specimens of Nccrophorus are about letting down a carcass [of
a small mammal or bird], one hears distinctly that they during
the work underground communicate mutually by the language
of stridulation. The sound is now higher and hasty, now deeper
and smoothered, and on the whole modulated in tlie most
manifold way. Sometimes a pause is suddenly interrupted by
a single sharp tone instantly answered by a similar one from
another specimen or simultaneously from se\'eral specimens.
Stridiilatioii iu Crustacea Decapoda. 65
and one gets the impression of the different moods agitating
the animals during the pains of the work: eagerness, impatience,
fretfuhiess, weariness, exultation; and sometimes the whole
company makes a kind of chorus-cry for the measured regula-
tion of the work".
And let us now turn to the stridulating organs in such forms
as the terrestrial crabs Ocypoda ceratophthalma and 0. macrocera
described above. It is instantly seen that they are more
highly developed than, for instance, those inNecropho-
rus, because they in the first-named species can produce two
\-er\- different tones, in the latter form even three tones. Whether
the animals really use this faculty is unknown (see p. 62), but
it may be supposed that they occasionally do so. And the topic
is, in my opinion, very interesting. But well planned — and,
for the rest, probably somewhat difficult — observations of
stridulating Decapoda and above all of species of Ocypoda with
highly developed organs are needed ; I even hope that this little
treatise may create interest in some Zoologist, who has an oppor-
tunity for biological obser\'ations in the field or perhaps in a
good "terrarium".
ON THE POSTEMBRYONIC OCCURRENCE
OF THE MEDIAN "DORSAL ORGAN" IN
CRUSTACEA MALACOSTRACA
I. Introductory Remarks.
In a paper on Sergcstcs (Proc. Zool. Soc. I^ondon 1896) the
present author wrote in the description of the youngest Masti-
io'o/)ws-stage of S. arcticus Kr. : "just is front of the gastro-hepatic
groove is observed a short protuberance in the median Hue".
— In his valuable paper: Zur Kenntnis der Metamorphose
von Sergcstes arcticus Kr. (Zool. Anz. Bd. XXXIII, 1908)
E. Wasserloos writes (p. Ji8) in the description of the second
Protozoea-stage : "In der Mittellinie des Cephalothorax bemerkt
man iiV)er dem Gehirn und dem Naupliusauge eine linsenartige
Her\'orwolbung des Chitins .... die bisher bei keiner Sefgcstes-
Larve ausser bei einigen Mastigopen \-on Sergcstes arcticus von
Hansen beschrieben worden ist An Schnitten habe icli
ausser der Chitinbucht und der darunter liegenden, allerdings
undeuthche Matrix nichts wahrgenommen Bine genaue Be-
schreibung und genaue Angaben iiber die erwahnte Hervorstiil-
jjung kann ich nicht geben, doch mochte ich eine Vermutung
aussprechen: Die Lage des Organs iiber dem Naupliusauge und
der Um.stand, dass es mit der Zuriickbildung des Naupliusauges
ebenfalls verschwindet, lassen es als wahrscheinlich erkennen,
dass die Protuberanz als Sammellinse fitr das Naupliusauge
dient". His suggestion on the function of the i)r()tul)erance is
certainly erroneous.
While working out the rich collection of Sergestidie collected
1)y tlie Prince of Monaco, I obser\ed the dorsal ])rotuberance in
The "dorsal or^an" in Crustacea Malacostraca. 67
Acanthosoma-stages of five species and in young Mastigopus-
specimens of several species, furthermore a rudiment of the same
organ in adult specimens. The idea struck me that it must be
the so-called "dorsal organ" known in embryos of Crustacea
of most orders, but unknown in almost all adult Malacostraca
and in larvae of the same sub-class. In examining adults of a
good number of species belonging to all orders of Malacostraca,
I was surprised that the dorsal organ, though frequently looking
only as a rudiment, exists in some or several representatives of
most orders. It is found on the surface most frequently nearly
vertically above the mandibles or their base.
II. On our earlier Knowledge.
Nearh- all original observations on the dorsal organ are
scattered in papers very different in contents, though the
majority deal with embryolog}^ or development. In 1904 W. T.
Caiman's excellent hand-book on Crustacea was published; in
1913 W. Giesbrecht's part on Crustacea in Lang's Handbuch
der Morphologic was edited. These careful authors had written
"records" on the Carcinology during a number of years and
were uncommonly well versed in the vast literature; the state-
ments of both authors together in the books mentioned on
the occurrence of the dorsal organ may therefore be considered
nearly sufficient, and an extract is given here.
On Anaspides (the order Anaspidacea) Caiman writes (p.
164) : "On the dorsal surface [of the head], in front of the cervical
groove, is a pigmented area with a circular central spot sur-
rounded by four minute pits. The significance of this structure
is quite unknown, but it may be comparable to an obscure
"dorsal organ" apparently glandular in nature, occupying a
similar position in certain other Malacostraca". It may be point-
ed out, that Caiman in his treatment of the other orders of
Malacostraca does not mention the occurrence of a "dorsal
5*
68 Studies on Arthropoda. I.
organ" in the adult of any other form, but possibly he refers
in the lines quoted to the organ found in embryos of other
orders. — On the Tanaidacea he says (p. 194) : "A paired "dorsal
organ" is present" in the embryo; on p. 213: "A "dorsal organ"
is present in many Isopod embrj'os, and assumes very different
forms", which are mentioned. On the Amphipoda (p. 237) :
"A "dorsal organ" is early developed as a median thickening
of the ectoderm . . . . " — On the embryo in Mysidse (p. 179 — 80) :
"A pair of lateral thickenings of the epiblast appear \-ery earl)'
and, approaching each other on the dorsal side, fuse to form an
invaginated "dorsal organ"." But I may remark that Nusbaum
und W. Schreiber in 1898 (Biolog. Centralbl. Bd. 18, p. 742)
figured a transverse section of an embryo of My sis Lamorna'
showing the unpaired dorsal organ and a pair of dorso-lateral
organs, and all three organs have already begun to degenerate.
— At the Nebaliacea, Cumacea, Euphausiacea, Decapoda, and
Stomatopoda Caiman does not mention any dorsal organ.
Giesbrecht writes (p. 156 — 57) that not only in Cladocera
but in "vielen anderen Crustacea ein anderes Organ von meist
driisiger Struktur, ebenfalls in der Dorsalwand des Kopfes, das
aber nur transitorisch (bei lunbryonen, seltener Larven) auftritt
und sich meistens schon friili zuriickbildet ; das ist die Nacken-
driise (Nackenorgan, Nackenschild, Dorsalorgan . . . .)". Among
the Malacostraca it is found early in the embryo in Arthro-
straca (consequently Tanaidacea, Isopoda, and Amphipoda),
in Cumacea, Mysidacea, perhaps also some Decapoda; "bei Lep-
tostraken scheint es eine unpaarige Leiste zu bilden"; finally
"als Nackendriise aufgefasst wird auch .... eine dorsale
Driisenscheibe in the Maxillargegend von jungen und adulten
ICuphausien etc.". I have been unable to find in the special
literature on the Euphausiacea any statement on the organ.
In a small paper published in Jouni. Linn. Soc. Lond. vol.
XXIX (1903) the ]jre.sent writer ])ointed out an organ on the
The "dorsal organ" in Crustacea Malacostraca. 69
surface of the head near the posterior margin in the Isopod
Bathynomus giganteus; the organ — which shall be mentioned later
on — was briefly described, figured and compared with the organ
discovered by Caiman (1896) in Anaspides tasmanice; it was
added, that I had found a vestige of the organ in the allied form
Cirolana borealis. — The statements in the literature on the
organ in larv'se of Sergestes arcticus are quoted above.
Let us sum up. The median dorsal organ has been found
in embryos of representatives of the following orders of Mala-
costraca: Nebaliacea, Mysidacea, Cumacea, Tanaidacea, Isopoda,
.\mphipoda and perhaps some Decapoda. The Embryologists
tell us that it, at least generally, is of glandular nature and dis-
appears early; on its function nothing is known, besides it is
unknown in the embryo of Stomatopoda. — In adult forms it
has been found in Anaspides of the order Anaspidacea; in Ba-
thvnomiis and a species of Cirolana of the order Isopoda; finally,
according to the quotation from Giesbrecht, in young and adult
forms of the order Euphausiacea. In larval stages it is only
known in Sergestes arcticus.
III. The "dorsal organ" in adult Malacostraca
and some larvae.
It has not been my intention to inspect every genus avail-
able, but types of families or genera have been selected and
examined with a good pocket-lens ; it was found that within the
same family, sometimes even within the same genus, an organ
could not infrequently be discovered in a large species, but not
with any certainty in small forms. The following enumeration
shows that the organ has a much wider occurrence than might
have been supposed.
I. Nebaliacea.
Nehalia bipes O. Vabi. — In turning the animal a little to
and fro so that the light changes on the smooth, shining dorsal
JO .studies on Arthropoda. I.
surface of the head it is generally possible to perceive a faint
vestige of a median protuberance situated not inconsiderabh-
behind the base of the movable rostral plate.
2. Anaspidacea.
Anaspides tasmanice G. Thonis. — Caiman described and
figured a very conspicuous dorsal organ (Trans. Roy. Soc.
Edinburgh, XXXVIII, 1896). Nothing is to be added.
Paranaspides lacustris Geoff. Smith. — The organ is more-
reduced than in Anaspides, as there is no pigmentation; the ver\
small pits are irregularly arranged, and their number in three
specimens varies from 3 to 5.
3. Mysidacea.
Gnathophausia. — In a gigantic specimen of G. ingcus Uohrn
a part of the dorsal keel a little in front of its base and about
15 mm. long is flattened above and behind the middle distinctly
thickened, this narrow area has a pair of very conspicuous,
very oblique, convex spots marked off all around b>- an de-
pression, and the spots look almost as scars. In G. zuea Will.-
Suhni about one mm. of the dorsal keel above the mandibles
is, seen from above, rather considerably thickened but not flat ;
seen from the side with the light transmitted the dorsal chitinc
of this part is thin and the contents opaque, indicating that the
tissue is of another quality than in the surroundings.
Eucopia. — In one specimen of E. sculpticauda h'axon a
nearly circular, somewhat shallow depression situated above
the mandibles somewhat in front of the anterior transverse
furrow; the depression has a minute, dark point as if a scar
after a ])rick with a needle. In another specimen the depression
is wanting, but the dark point exists; in a third specimen noth-
ing could be seen with certaintw In specimens of E. ungui-
cnlata Will.-Sulnn nothing was found.
The "(lorsal oryan" in Crustacea Malacostraca. 71
1_
Lophogaster. — In L. typiais M. Sars no vestige is discover-
able.
Borcomysis. — B. scyphops G. O. S. has somewhat in front
of the gastric groove a moderately large and rather shallow
depression, at the middle of which is seen a somewhat low, a
little oval, rounded and \-er\' distinct protuberance with one
to three minute pits. — B. nob His G. O. S. has very near the
gastric groo\'e a small but rather high, a little oval protuberance
without visible pits. — B. microps G. O. S. has a little in front
of the gastric groove a conspicuous, nearly semiglobular, smooth
protuberance.
Of the subfamily Mj'sinas two moderately large forms, viz.
Mysideis grandis Goes and Mvsis mixta Lilljeb., have been
inspected, but no vestige of any organ was found.
4. Cumacea.
Some few larger forms ha^'e been examined, but nothing
could be found.
3. Tanaidacea.
Some large specimens of Apseudes and Alaotanais, thus
representatives for both families of the order, have been in-
spected with negative result.
6. Isopoda.
Idothea. — In /. balthica Pall, is frequently found near the
posterior margin of the head a very small area a little broader
than long, and with a few tiny pits or, in one specimen, with
impressed transverse lines; the area is generally a little or
somewhat depressed, but in one specimen it is larger than usual,
raised and shining. In a well-sized specimen from Iceland the
area is uncommonly conspicuous, moderately large, very slightly
depressed, shining, with a large, oblong pit in the middle, and
72 studies on Arthropoda. I.
around this 8 or 9 extremely minute, oblong pits. — In /. cmar-
ginata F. and /. ungulata Pallas organs somewhat similar to
those in /. halthica are found.
Among other animals belonging to the sub-order Valvifera
Mesidothca sibirica Bir., M. Sahini Kr., and Arcturus Baffin i
Sab. have been inspected, but with negative result.
Scrolls. — S. paradoxa Fabr. has a very distinct though
somewhat small, a little oblong, depressed area near the posterior
margin of the head; the area has several tin}' pits, especially
near the masgin. — .S. Schythei Ltk. has a similar nearly circular
area.
Bathynomiis. — In B. giganteus A. M.-Edw. an organ was
discovered, briefly described and figured by me in 1903 (see
p. 68). I have examined a large immature female. Near the
posterior margin of the head it has a most conspicuous, whitish
spot, which does not show the numerous, irregularly impressed
points on the surrounding brownish chitine. The spot is as a
whole a little arched but depressed along the middle; each half
has a small group of 6 or 7 minute pits; the median part has a
x'ery oblong area well marked off by an depressed line and with
a linear depression in the median line; somewhat behind each
group of pits is found a shallow excavation which has a number
of oblique, parallel, impressed striae; at the front end of the area
is seen a group of some nearh' rudimentary pits.
Cirolana. — In C. borealis Lilljeb. a \ery small group of three
to six tiny pits is found near the posterior margin of the head;
they are sometimes situated in a very shallow or very distinct
depression. — A specimen of C. Rossii Miers has some irregularly
scattered minute pits.
^ga psora L. and specimens of Rocinda, Anilocra and Cy-
mothoa have been inspected with negative result.
Among the sulvorder Asellota Asellus aquaticus L., Mun-
nopsis iypica M. Sars and Muniuypsurus giganteus G. O. Sars,
The "dorsal organ" in Crustacea Malacostraca. 73
among the Oniscoidea Ligia oceanica L. and the gigantic Tylos
granulatiis Krauss have been examined without finding any
vestige of the dorsal organ.
7. Amphipoda.
Large specimens of genera comprising forms of very consider-
able size, as Aiionyx, Stegocephalus, Gammarus, Maera, have
been inspected, but the result was absolute negative.
8. Euphausiacea.
Thysanopoda. — In T. egregia H. J. H. the gastric keel —
between the front margin and the gastric groove — has somewhat
behind the middle a short part raised rather considerably^; this
part is cut off horizontally so that its upper surface is flattened,
and this surface shows an aspect different from that of the
surrounding integument. (The raised part is shown in fig. 21
in my paper on Schizopoda in Bull. Mus. Ocean. Monaco, no.
30, 1905, p. 23) — T. cornuta Illig shows a similar structure. —
In T.cpgualis H. J. H. nothing could be perceived. — T. microph-
thalma G. O. S. has a feeble vestige on the gastric keel which
on its highest part is a little flattened above.
In Bentheuphausia amhlyops G. O. S. a vestige is scarcely
perceptible.
In Meganyctiphanes norvegica M. Sars the gastric keel has
a somewhat high and rather short part thickened upwards with
the dorsal surface distinctly flattened; seen from the side with
transmitted light the contents of the raised part is generally
lighter than the surrounding tissue.
Euphausia. — In E. superha Dana the median keel is at some
distance in front of the gastric groove more or less distinctly
raised and thickened, and at each side of this part the surface
of the carapace is distinctly excavated, but the keel itself is
rounded above without vestige of any special structure.
74 Studies on Arthropoda. I.
' In E. KroJinii Brandt no \'estige.
In N ematohrachion boopis Calm, and Ncmatoscelis mcgalops
G. O. Sars the gastric crest is at its highest point slightly angular
and shows a vestige of the organ ; seen from the side with trans-
mitted light the contents of that part of the keel is lighter than
the surrounding tissue.
lyarvse. — Some larva? belonging to the genus Euphausia
have been examined, but it was not possible to discover ain-
rudiment of a dorsal organ. At a future occasion I will have to
examine the vast material of larval forms secured together with
adults in the North Atlantic by the Prince of Monaco, and then
there will be a good opportunity to look for the dorsal organ in
representatives of almost all genera.
q. Decapoda.
The dorsal organ is found in the adults of most species of the
Penaeida? inspected by me, and in all genera and species of the
Sergestidse excepting Lucifer. Furthermore it was detected in
several genera of the Caridea. Besides it was disco\ered in cer-
tain larv^al stages of the genus Scrgcstcs and in a few larvae of
Penseida?. In the following an account shall be given, but as to
the genus Sergestes a brief abstract may be sufficient, because
in a monograph of the North-Atlantic species secured by the
Prince of Monaco and now in composition a more detailed report
will be embodied. — In vain I have looked for the organ in a
species of the genus Cambanis, and it is scarcely to be found in
Astacidse, Palinuridse, Galatheidse, etc. or in the crabs.
A. Pena'idte.
Aristeus. — A. Edwardsianus Johns, has a little behind the
first dorsal spine the median keel thickened with its ui)per
surface expanded ; ni the middle of this part is found a somewhat
oblong area well marked off by a depression, this area has
The "dorsal organ" in Crustacea Malacostraoa. 75
slightly before the middle an oblong, dark-brown spot sharph'
defined and with at least one minute pit. — In .4 . scmidentatus
Bate is found a moderately small but uncommonly deep de-
pression a little behind the first dorsal spine; the depression has
a small, circular, somewhat convex area behind the middle.
Solenocera Agassizii Fax. — A little behind the first dorsal
spine an oblong, rather depressed area with a small knot at the
middle.
Pencens. — P. setijerus L. has considerably behind the first
dorsal spine a proportionately somewhat long part of the median
keel thickened and flattened above or even longitudinally a
little excavated ; the broadest part of that area has in one spec-
imen an oblong pit, in another specimen nothing. It must be
remarked that the area in question is situated more backwards
than in any other genus of the Malacostraca. — In P. caramotc
Risso nothing could be discovered.
Larvae. — In a gigantic larva in the Myszs-stage, measuring
20.5 mm. from the tip of rostrum to the end of telson and cap-
tured in the Pacific, a small, oblong and rather low protuberance
is easily seen a little behind the origin of the rostral keel. —
In a larva in an older Mys/s-stage, belonging to a quite different,
somewhat small type, an oblong and somewhat high protuber-
ance is found a little in front of the gastro-hepatic groove; seen
from the side the protuberance is directed upwards and forwards ;
the larva is from lat. 4^/3° N., long. 1071/,° E.
B. Sergestidse.
Sergestes. — The organ has been found in adult specimens of
everyone of the 15 species hitherto captured north of equator,
but it could not be seen in every specimen of some of the smaller
species, as S. mollis Smith, S. arcticus Kr. , S. atlanticus M. Edw.,
S. vigilax Stimps., and S. Edwardsii Kr. The organ is situated
a Httle or somewhat in front of the gastro-hepatic groove. It
76 studies on Arthropoda. I.
is a small or very small area, in most cases distinctly or consider-
ably raised as a rounded, nearly circular or transYerse-o\'al
protuberance, sometimes, but far from always, marked off b}'
an depressed line; in a few cases the whole area is depressed.
Frequently the area has a ver>'' distinct granule or raised point
in front of the middle, in other cases a few tiny pits or no pit
could be made out. In a few cases the area is brown, but gener-
ally of the same colour as its surroundings. There is also some
individual variation in the area as to its height or the depth of
its surrounding impression.
Petalidium. — In one specimen of P. obesuni Kr. is found a
moderately small, a little oblong and feebl}' elevated area with
a tiny and more raised point in front. In some specimens an
area was not discoverable with certainty, but the quality of the
integument makes the investigation difficult and uncertain.
Sicyonella. — In one specimen of 5. maldivensis Borr. a
distinct, small group of fi\'e minute pits close behind the dorsal
crest; in another specimen the group has nearly vanished.
Acetes. — In one specimen of A. vulgaris H. J. H. a group of
six minute pits close together and somewhat in front of the
rudimentary^ gastro-hepatic groove; in another specimen a
rudimentary^ protuberance with vestiges of a few pits.
Lucijer. — No trace of any organ.
Larvae of Sergestes. — As mentioned above (p. 66) Wasser-
loos discovered the dorsal organ — but did not inter])ret it as
such — in the second Protozoea-stage and the Acanthosoma-
stages of 5. arcticus Kr. ; the present writer had found the
protuberance in question in the youngest Mastigopus of the same
species. The dorsal organ is an erect or distinctly ])rocurved,
rounded protuberance in the Atlantic Acanthosoma-stag'^s known
to me and belonging to .S". arcticus Kr., S". tcniiiremis Kr., .S". ro-
bustus Smith, .S. c<)r)iicnlitni Kr., and .S". vigilax Stimps. ; the
protuberance is generally easily seen from llie side. It is also
The "dorsal organ" in Crustacea Malacostraca. 77
found in the younger Mastigopus-stages of several and probably
all species, but it differs sometimes considerably in aspect, as
in S. pectinatiis Sund it is shaped as a thick, short spine directed
obliquel}' forwards. In the older lars'al stages it has apparently
disappeared, but 3'et it exists in all probability, because it is
found in adult specimens, though its aspect is quite dif-
ferent; I have not undertaken the certainl}^ difficult inve-
stigation of the dorsal integument in front of the gastro-
hepatic groove in older lar\'?e or very young specimens with
black eyes.
Larvae of Lucifer. — In the youngest Mys?'s-stage —
without pleopods — of L. Faxonii Borr. a rather large and
considerably vaulted dorsal protuberance is found above the
base of the mandibles ; it is not marked off in any way from the
surrounding integument, and I am unable to decide whether it
is homologous with the very characteristic protuberance in the
Acanthosoma — or Mys/s-stages — of Sergestes. In older stages,
with pleopods, the protuberance is proportionately^ smaller.
C. Caridea.
Acanthephyra muUispina Cout. — A little behind the first
dorsal spine the median line has a small, circular depression sur-
rounding a more or less distinct protuberance.
In Nematocarcinus exilis Bate a very smaU organ close at
the base of the first dorsal spine.
In Ephyrina sp. from the North Atlantic the anterior crest
of the carapace is somewhat from its base flattened above with
a small but ven,^ distinct, circular, rounded protuberance, the
surface of which has two or three pits so tiny that they could
not be counted with certainty.
Pasiphae. — In P. principalis Sund the dorsal keel is distinctly
thickened considerably behind the rostrum, but a protuberance
is wanting and no pit could be discovered. — A young P. sivado
yS studies on Arthropoda. I.
Risso about 13 mm. long lias a just perceptible, rudimentary
protuberance considerably behind the rostrum.
In Spirontocaris microceros Kr. an area marked off by
a circular depression very near the base of the first dorsal
spine.
In Bythocaris Icucopis G. O. S. a distinct rudiment in the
keel a little behind the first spine.
In Alpkeus avams F. a small, but well developed depression
a little or slightly behind the median keel.
PalcBmon brasilicnsis Hell., Pandalus Bonnicri Caull. and
Pontonia sp. have been inspected with negative result.
10. Stomaiopoda.
To begin with it may be remarked that moderately large to
\'ery large specimens of the present order have frequently the
surface of the median part of the carapace more or less rubbed
and are consequently badly fit for the investigation, as in such
cases the dorsal organ is frequently difficult or impossible to
point out with certainty.
The dorsal organ has been mentioned in descriptions — and
besides shown in figures — of some species of the genus Squilla
by at least two able Zoologists, viz. Stanley Kemp in his excellent
memoir on the Indo-Pacific forms of the order (1913) and by
Caiman (1917). They name it the "dorsal pit", which is only
a descriptive term, as they did not recognize what this pit
really is. — It may also be pointed out that Giesbrecht in his
useful, extremely elaborate, long-winded and as to literature
not always \'ery fair monograph of the Mediterranean Stomato-
poda (1910) has not observ^ed the "dorsal pit", though it is con-
spicuous in the common Squilla mantis h., at least sometimes
not difficult to see in .S". Desniarestii Risso, and ought at least
to have been indicated on his large figures of the carapace of
these two species.
The "dorsal organ" in Crustacea Malacostraoa. 7Q
Squilla. — In .S. mantis L. the median keel is considerably
widened and flattened above somewhat behind the bifurcation
and far in front of the mandible; the widened, rather short part
has a very oblong depression, the bottom of which is a little
convex and looks as pricked feebly with a needle. — In 5.
raphidea F. the organ is conspicuous and nearly as in 5. mantis.
— In 5. Desmarcstii Risso was found in two of four specimens
examined a small, circular, low depression with a rudimentary
median pit; the depression is situated considerably in front of
the mandibles. — In 5. gibba Nobili the median carina is flattened
and much widened a little behind the middle and has there a
small, a little oblong, convex area surrounded by a rather deeply
depressed ring, and placed a little in front of the mandibles.
Lysiosquilla. — In a rather large specimen of L. cusebia
Risso a very small and feeble depression a little in front of the
middle of the carapace above the mandibles; in another rather
large specimen and in small specimens nothing could be observed.
— In L. maculata F. no vestige was found.
Pseudosquilla ciliata F. — In two specimens a nearly circular,
\-ery conspicuous and somewhat deep depression with two or
three tiny pits on the flat or a little convex bottom, situated a
little in front of the middle of the carapace and somewhat in
front of the mandibles. In a third specimen the depression is
small and shallow, in a fourth quite rudimentary'.
Odontodactylns scyllarus L. — Slightly behind the middle of
the carapace a rather large, moderately shallow depres-
sion, in the middle of which a small, circular, somewhat convex
area.
Gonodactylus Oerstedii H. J. H. — A deeper or more shallow,
small, circular, depressed area a little behind the middle of the
carapace and above the mandibles. In young specimens the
depression is either considerably more feebly developed or not
discernible.
So studies on Arthropoda. I.
Larvae. — Specimens of Alima, Pseuderichthus and Lvsic-
richthus, also the first stage, have been inspected, and the result
was always negative.
IV. Summary.
The preceding chapter shows that the "dorsal organ" can
be observed on the posterior part of the dorsal surface of the
head or on the carapace in adults of some or several genera of
all orders of Malacostraca, excepting in Cumacea, Tanaidacea
and Amphipoda. Whether it sometimes or frequently or even
generally has a special function must be made out by a student,
who has a good material either of living animals or of specimens
especially preserved for histological research, for cutting b>-
microtome. As the organ has such wide occurrence, it is no very
probable that it has no function in the adult. And this sup-
position is strenghtened by the fact that it exists in many and
probably in most adult Stomatopoda, but seems to be wanting
in their larvae; that it should exist in the embrj^os of this order
— on which nothing is known — then be absent in the larvae
but reappear in the adults, is highly improbable. We are in
reality completely ignorant on the significance of the dorsal
organ both in embryos, in larvic and in adults, so ignorant
that it seems scarcely possible to produce even a hypothesis.
Perhaps experiments on living animals similar to those carried
out by some authors in order to investigate the excretor\'
system might yield some result.
^itvrli'es otv AriiidMp'OrMJ/. I.
Pi I
ti^AXzye/ <fty
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Ph. E.
l.Trithifpeu^ hr^e^iAcaada/ luap. 2. Crifpiostemma/ cruj.^si^alpe/ H.t^S.
3 . C. /te«e/ rv. sf.
H. J. Hansen/ Aei'. BrA^tT,^ s,ca
studies on Arihropo4iay I.
Pl.JK.
': W
no. JJ.anfs&n^ ^M Briize^ s<y.
lb
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