286 



ZOOLOGY. 



and Europe, which we have called Syncarida, and 

 which have antennae and tails like shrimps, but the body 



Pig. 249. Gampsonyx firribriatus of European coal measures, 2)4 times natural 



and limbs like Amphipods. In the Isopods the body is flat- 

 tened and the head rather broad. 



Fig. 251 is a dorsal view of Serolis Gail-, 

 dichaudi Audouin and Edwards, with the 

 two pairs of antennae and pointed sides of 

 each thoracic segment, dissected to show the 

 nervous system, the two pairs of antennal 

 nerves; the optic nerves (op) sent to the 

 compound eyes. Fig. 252 represents a trans-* 

 verse section of the body, showing the mode 

 of insertion of the legs, and the equality in 

 the tergal and sternal sides of the body. 

 Fig. 254 represents a gill. In the common 

 pill-bug (Porcellio) aerial respiration is per- 

 formed by respiratory cavities situated in 

 the abdomen. In Tylos similar cavities are 

 filled with a multitude of branching coeca, 

 serving for aerial respiration, thus antici- 

 pating the tracheary system of insects. 

 , I The nervous system is quite simple. (Fig. 



\\ // 250, Idotcea, and Fig. 251, that of Serolis.) 



V/ =5 \~y ?s ^/ The digestive canal is straight, consisting 

 Fig. 250. Nervous of a short oesophagus, a membranous stom- 

 m^-SiSS^f: ach, and usually a short tubular intestine ; 

 s.Kingsiey. ^ jj ver cons i s ti n g o f several short creca. 



In Serolis Gaudicliaudi the stomach is somewhat pear- 



