THE CARBONIFEROUS PERIOD. 18I 
ecapods (Brachyura), in which the abdomen is short, not 
terminated by a tail-fin, and tucked away out of sight beneath 
the body, is at present not known to be represented at all in 
the Carboniferous deposits. 
In addition to the water-inhabiting group of the Crustaceans, 
we find the articulate animals to be represented. by members 
belonging to the air-breathing classes of the Avachnida, Myria- 
poda, and Insecta. The remains of these, as might have been 
expected, are not known to occur in the marine limestones of 
the Carboniferous series, but are exclusively found in beds asso- 
ciated with the Coal, which have been deposited in lagoons, 
estuaries, or marshes, in the immediate vicinity of the land, and 
which actually represent an old land-surface. The Avachnids 
are at present the oldest known of their class, and are repre- 
sented both by true Spiders and Scorpions. Remains of the 
latter (fig. 123) have been found both in the Old and New 
Fig. 123.—Cyclophthalmus senior. A fossil Scorpion from the Coal-measures 
of Bohemia. 
Worlds, and indicate the existence in the Carboniferous period 
of Scorpions differing but very little from existing forms. The 
group of the JZyriapoda, including the recent Centipedes and 
Galley-worms, is likewise represented in the Carboniferous strata, 
