P sen do sco rpion es. 105 
by a single plate, which, however, sometimes shows traces of Table-case 
segmentation. There are no median eyes, but one or more lateral No - 
ocelli may be present. The fingers of the chelicerae are furnished 
with delicate membranous structures called the “ serrula ” and 
“ lamina ” respectively. The movable finger of the mandible is 
furnished with a branched or styliform structure called the “ galea,” 
or with a little terminal tubercle ; and it is on this structure that 
the orifices of the silk-glands debouch. The palps are large and 
chelate, as in the scorpions. There is no constriction between the 
cephalothorax and the abdomen (opisthosoma), but the large dorsal 
plate of the praegenital segment (which is generally suppressed 
in the Euarachnida) lies between these 
two regions. Eleven abdominal somites 
can often be distinguished, and none of 
them are narrowed to form a tail, but 
the last of them is very small and is 
often hidden within the segment which 
precedes it. 
The Pseudoscorpions are small 
Arachnids, which live under stones or 
the bark of trees or in moss. They 
are occasionally found in houses, 
amongst books, etc., and several species 
have been found on merchant-ships ; 
not uncommonly specimens may be 
met with clinging to the legs of flies or 
beneath the wing-cases of beetles. One 
of the British species ( Obisium mari- 
timum ) is found under stones or beneath seaweed below high-water 
mark. Their food consists of mites or small insects. At the 
breeding season the female envelops herself and her eggs, which 
she attaches to the under side of her body, in a spacious silken 
cell. 
A similar cell is spun as a protection whilst the animal is 
moulting and during hibernation. 
The earliest-known fossil forms of Pseudoscorpions are from 
amber deposits of Oligocene age. At the present day the group 
is distributed all over the temperate and tropical countries of the 
world. 
It is divisible into two sub-orders : (1) Panctenodactyli, 
(2) Hemictenodactyli. Drawings illustrating the main points of 
difference between these sub-orders are placed in Table-case 24. 
Fig. 68. 
Chelifer cancroides, x 5. 
(After Berlese.) 
