2 THE BRITISH WOODLICE. 
which has been named Archeoniscus brodiet, and is said to be 
referable to the recent family Aegidae is found in some numbers 
in the Purbeck Beds (Upper Jurassic), of this country (47). 
Fossil Isopods have also been recorded from the Oolite and 
from the Oligocene (Isle of Wight). 
Turning to the Woodlice proper, we find’that they first make 
their appearance in the Miocene (of Oenigen and Baden), and 
occur also in amber (79); while examples of genera, such as 
Oniscus and Porcellio, have been discovered in late Tertiary 
deposits (47). 
External structure and appendages.—Woodlice agree 
Lateral Bas 3 HEAD ° 
Laterat Mira ®))  aspomen 
Plates ee (aelasome) 
< 
Lelsorn” 
FIG. I.—PARTS OF THE BODY. 
(Omscus asellus.) 
in being of a somewhat oval form, and their bodies are arched, 
the curve varying in different genera and species. A head is to 
be distinguished ; behind this comes the thovax of seven segments 
which are often considerably broader than the six succeeding 
ones which form the abdomen (see fig. 1.) 
The head carries two large antennae (fig. 3) 
which are very evident, and a careful search 
with a lens will reveal a second and minute 
pair (the smalley antennae) situated between the 
base of the others, and really anterior to them. 
(figs. 2 and 4.) 
The larger antennae are customarily bemt "2. see mmet 
ANTENNA. 
at certain points, and we can distinguish a — (miseus asellus.) 
