MYRIAPODA. 183 



mously-developed pair of nipping-claws (fig. 124), and the 

 antennae are also converted into chelae. The head carries six, 

 eight, or twelve simple eyes, and the last joint of the abdomen 

 (telson), terminates in a hooked claw, perforated for the trans- 

 mission of the duct of a poison-gland. 



As regards their distribution in time, the Scorpions com- 

 mence in the Carboniferous period, where they are represented 

 by the genera Eoscorpius and Cydophthalmus. The most 

 celebrated fossil Scorpion is the Cydophthalmus senior (fig. 125) 

 of the Bohemian Coal-measures. This remarkable form re- 

 sembles the living Androctonus in having twelve eyes, but 

 these are disposed in a circle, whereas in the latter there are 

 six eyes on each side of the head. 



ORDER ARANEIDA. This order includes the true Spiders, 

 which are characterised by the amalgamation of the head and 

 thorax into a single mass, to which the generally soft and unseg- 

 mented abdomen is attached by a constricted portion or peduncle. 

 Respiration is effected by pulmonary sacs in combination with 

 air-tubes (tracheae). The head bears from six to eight simple 

 eyes. 



The oldest-known Spiders occur in the Carboniferous Rocks. 

 In the Coal-measures of Upper Silesia, Romer has described a 

 Spider, which is allied to the living Lycosa, and which he has 

 termed Protolycosa anthracophila. Other fossil Spiders have 

 been described from the Lithographic Slates of Solenhofen 

 (Middle Oolite), and from the Tertiary Rocks, and a good 

 many species occur preserved in amber. 



CLASS MYRIAPODA. 



The Myriapods are Articulate animals in which the head is 

 distinct, and the remainder of the body is divided into nearly 

 similar segments. There is no marked boimdary-line betweeji the 

 thorax and abdomen, and the segments of the latter carry locomotive 

 limbs. There is one pair of jointed antennas, and the number of 

 legs is always more than eight pairs. Respiration is effected by 

 air-tubes (trachea^. 



The living Myriapods are divided into the three orders 

 Chilopoda, Chilognatha, and Pauropoda. In the Chilopoda are 

 the Centipedes, characterised by their masticatory mouth, and 

 carnivorous habits, by the possession of legs in single pairs 

 (usually from fifteen to forty pairs), and by having antennae of 

 from fourteen to forty or more joints. In the Chilognatha are 

 the Millipedes and Gallyworms, characterised by their vege- 

 tarian habits, by having the segments of the body so amal- 



