prevailing forms being oval, cordate, and quadrilateral. The anterior region, where the eyes
are situated, is frequently elevated, and is sometimes tuberculated. The covering of the
inferior portion of the cephalo-thorax, or sternum, likewise consisting of a coriaceous plate, is
oval, circular, or cordate. It is scalloped on the lateral margins, and often presents small
eminences opposite to the articulation of the legs. Both these parts are densely clothed with
hairs in some species, but in others they are almost entirely without hairs, smooth, and
glossy.
All spiders at present known have two, six, or eight smooth eyes, which vary much in
size and relative position, supplying characters of great importance in the systematic arrangement
of species.
The falces, inserted immediately under the anterior margin of the cephalo-thorax, though
modified in form, are, for the most part, subconical; and have usually at the extremity of
their inner surface a longitudinal groove provided with sharp teeth on the sides, which receives
the fang when in a state of repose. The fang is very hard, curved, acute, and has a small
fissure near the point, which emits a colourless fluid secreted by a gland. These instruments
are either glabrous, or covered more or, less with hairs, and are sometimes armed with sharp,
corneous points, particularly at the extremity, near the insertion of the fang.
Spiders belonging to the family Mygalidce have the falces articulated horizontally, their
movement being vertical; the,falces. of those inpluded in the other families being articulated
vertically, or on an inclined plane, and their principal movement lateral, with the exception of
a few species whole falces are united.
The maxillae and the sternal lip are directed forwards, or inclined downwards in all
spiders. The former are hairy, a t the extremity, which is round; obliquely truncated, or*
pointed. Their configuration and their position in relation to the sternal lip, together with
the form of the latter, furnish excellent generic characters.
Connected with the maxillae are the palpi, which project on each side of the falces. They
consist of five joints supplied with hairs and spines, and are, for the most part, terminated by
a curved, pectinated claw in female spiders. The first, or axillary joint, is short; the second,
or humeral joint, is long; the third, or cubital joint, is short; the fourth, or radial joint, which
is rather long in the females, is usually short in the males, and, in the latter sex, is frequently
provided with one or more corneous apophyses; the fifth, or digital joint, varies in iength;
but in the males it is commonly short, oval, and dilated, having the sexual or palpal organs
attached within and partially .concealed by a cavity on its under side,. These latter, organs,
composed of soft, membraneous, vesicular parts, susceptible of tumefaction, exhibiting on their
external surface, or at their extremity, various curved, corneous processes, are complicated in
structure and greatly diversified in form, indicating by their complete development a state of
maturity.
Much variety is observable in the figure of the sternal lip, which, as its name implies, is
connected with the sternum; the prevailing forms are oval, semicircular, quadrilateral, and
triangular. In the greater number of spiders this part is glabrous. Between the sternal
lip and falces the palate is situated, whose hairy extremity alone is visible in its natural
position.
The legs, disposed round the cephalo-thorax, are composed of a haunch of one joint.; a
thigh and a shank, each formed of two joints; and a foot, also divided into two joints; except
in the species belonging tö thé genus Hërsilia, which have the foot divided into three joints.
The haunch, or coxa, is articulated with the cephalo-thorax. The first part of the thigh, or
the exingüinal joint, is short, and is closely united' to'the haunch; the second part, or the
femoral joint, being long. The first part of the shank, or the genual joint, is usually short,
and is closely united to the second part, or the tibial joint, which is long. The parts of the
foot are the upper or metatarsal joint, and the lower or tarsal joint, Which latter is almost
always terminated by two or more claws. Two óf these c'laWsi, inserted one beside the other,
are in general curved, and pectinated, and immediately below them another frequently occurs;
it is small, and abruptly inflected near the base, where a pair or two of minute teeth may
sometimes be perceived. When the last claw is not present, a scopula or brush, consisting of
coarse, compound, hair-like papillae, often occupies the inferior surface, or the extremity of the
tarsi. Closely analogous to the tarsal cushions of insects in the function it performs, this
apparatus enables its possessor to ascend hard dry bodies having highly polished, perpendicular
surfaces, by the emission of a viscous secretion.1
In addition to the claws already deséribed, some spiders have several small, dentated
ones on the sides and lower part of the tarsi, at their êxtremity. This is the case with the
Epëirte in particular; they have also a strong moveable spine, inserted near the termination of
the tarsus of each posterior leg, on the under side, which curves a little upwards at its
extremity, and exhibits,a slight irregularity of outline at its superior surface. These spines,
which have been denominated sustentacula, subserve an important purpose. By the contraction
of their flexor muscles they ate drawn towards the foot, and are thus brought into
immediate opposition to the claws, by which means the. animals are enabled to hold with a
firm grasp such lines Us they have occasion to draw from the spinners with the feet of the
hind legs, and such also as they design tb attach themselves to.2
Like the palpi, the legs are provided in a greater or less degree with hairs and spines;
and some spiders, Cinijlo attox and Ergatis benigna, for example, have on the superior part of
the metatarsal' joint of each posterior leg two parallel rows of moveable spines forming a
curling apparatus, employed in the construction of their snares. This apparatus has received
the name of calamistrum.8 The relativé length of the legs presents much diversity, and is not
always alike even in the sexes of the same species.
In much the"greater number of spiders, the abdomen, attached to the cephalo-thorax by
a short pedicle, is enveloped in a soft, continuous skin, covered more or less with hairs; but
in some species its covering is of a hard, corneous consistency. The predominant forms of
the abdomen are ovate, cylindrical, and subglobose, variously modified; and its figure is still
further diversified in some species by fleshy tubercles and corneous spines. On its upper part
or back it frequently exhibits divers colours, arranged according to numerous designs, which
greatly contribute to the distinction of species.
Placed immediately below the anus are the spinning-mammulas; they are four, six, or
eight in number, conical or cylindrical in figure, composed of one or more joints each, and are
1 * Transactions of the Linnean Society/ vol. xvi, pp. 768, 769. ‘ Researches in Zoology/ p. 289.
‘Annals and Magazine of Natural History/ vol. xv, pp. 115-118.
2 ‘ Transactions of the Linnean Society/ vol. xvi, p. 476; vol. xvlii, p. 224, note.
8 Ibid., vol. xvi, pp. 471-475; vol. xviii, pp. 224, 606.