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family of spiders, Liphisiidae, in which the abdomen is segmented;
representatives of this family occur only in Hurtna and from Malay
Paninsula to Sumatra. In the genus Tetrablemma, found in Ceylon, the
abdomen bears a series of plates, which are evidently Spiders vestiges of a
segmented condition. But in all Indian spiders the abdomen is sac-like.
In spiders the cephalothorax, like the abdomen, is unsegmented,
although frequently the head and the thorax are slightly separated by a
furrow, the cervical groove. In such cases, most writers refer to the head as
the cephalic part, or the pars thoracica ; But the simple terms head and
thorax are sufficient for all purposes, and will be used when it is necessary
to refer to the principal divisions of the cephalothorax. The hard
integument forming the dorsal wall of the cephalothorax is termed the
carapace.
The head is that portion of the cephalothorax which bears the eyes and
so-called mouth-parts, the appendages that are used for seizing and
chewing the prey. It is either slightly or not at all separated from the thorax
; but it is almost always easily distinguished.
The abdomen is soft skinned and oval in form. Not infrequently it is
horny. The generative organs and the anterior pair of breathing-organs
open ventrally along a curved groove, the genital fold, which marks off the
fore part of the abdomen as the epigastric area. These breathing organs or
pulmonary sacs are covered by plates or opercula, and the integument in
front of the genital aperture is in many females horny and variously
modified to form an organ, the vulva or epigyne. The breathing organs of
the posterior pair are either operculate pulmonary sacs or tracheal tubes
with simple apertures, which rarely open sepa¬rately behind the genital
fold, but more commonly unite to form a single aperture situated iust in
front of the spinning mamillae.
There are usually three pairs of spinning mamillae attached to the hinder
end of the lower surface of the abdomen an anterior and inter-mediate and
FAUNA 509