500 
CLASS ARACHNIDA. 
The third family of the Trachean Arachnjdes, 
that of 
Holetra, Hermann , 
Has the thorax and abdomen united in a mass, under a com- 
mon epidermis ; the thorax is mostly divided into two, by a 
strangulation, and the abdomen presents only in some the 
appearances of rings, formed by some folds of the epidermis. 
The anterior extremity of their body is often advanced in 
the form of a muzzle, or bill. The majority have eight feet, 
and the others six. 
This family is composed of two tribes. 
The first tribe, that of Phalangita, Lat ., has very ap- 
parent forceps, either projecting in front of the trunk, or in- 
ferior, and always terminated by a didactylous pincer, pre- 
ceded by one or two articulations. 
They have two palpi in the form of a thread, of five articu- 
lations, the last of which is terminated by a small claw; two 
distinct eyes ; two jaws formed by the elongation of the radical 
articulation of the palpi, and often four additional ones, which 
are likewise nothing but a dilatation of the haunch of the first 
two pair of feet; the body oval, or rounded, covered, at least 
on the trunk, with a more solid skin ; some appearances of 
rings, or folds, on the abdomen. The feet, always eight in 
number, are long, and distinctly divided after the manner of 
those of insects. Many at least (plialangium) have, at the 
origin of the two posterior feet, two stigmata, one at each side, 
but concealed by the haunches. 
The majority live on the ground, on plants, at the bottom 
of trees, and are very agile ; others conceal themselves under 
stones, and in moss. Their sexual organs are placed under 
the mouth, and internal. 
