y cases, of eleven somites, the 11th somite
very small, often hidden within the both. Respiratory organs in the
form of tracheal tubes opening by a pair of stigmata in the 2nd and
3rd somites of the opisthosoma. Intromittent organ of male beneath
sternum of the 1st somite of the opisthosoma.

Sub-order a. Panctenodactyli.--Dorsal plate of prosoma (carapace)
narrowed in front; the appendages of the 1st pair small, much
narrower, taken together, than the posterior border of the carapace.
Serrula on movable digit of appendages of 1st pair fixed throughout
its length, and broader at its proximal than at its distal end; the
immovable digit with an external process.

Family--Cheliferidae (_Chelifer_ (figs. 70, 71, 72), _Chiridium_).
" Garypidae (_Garypus_).

[Illustration: FIG. 72.--_Garypus litoralis_, one of the
Pseudoscorpiones. Lateral view.

I to VI, of the six prosomatic appendages.
o, Eyes.
prae-gen, Tergite of the prae-genital somite.
1, Genital or first opisthosomatic somite.
2, 3, 10, The second, third and tenth somites of the opisthosoma.
11, The minute eleventh somite;
an, the anus.

(Original.)]

Sub-order b. Hemictenodactyli.--Dorsal plate of prosoma scarcely
narrowed in front; the appendages of the 1st pair large, not much
narrower, taken together, than the posterior border of the carapace.
The serrula or the movable digit free at its distal end, narrowed at
the base; no external lamina on the immovable digit.

Family--Obisiidae (_Obisium, Pseudobisium_).
" Chthoniidae (_Chthonius, Tridenchthonius_).

_Remarks._--The book-scorpions--so called because they were, in old
times, found not unfrequently in libraries--are found in rotten wood
and under stones. The similarity of the form of their appendages to
those of the scorpions suggests that they are a degenerate group
derived from the latter, but the large size of the prae-genital somite
in them would indicate a connexion with forms preceding the scorpions.
Reference to literature (37).

[Illustration: FIG. 73.--_Cryptostemma Karschii_, one of the Podogona.
Dorsal view of male.

III to VI, The third, fourth, fifth and sixth appendages of the
prosoma.
a, Movable (hinged) sclerite (so-called hood) overhanging the first
pair of appendages.
b, Fused terga of the prosoma followed by the opisthosoma of four
visible