286 



ZOOLOGY. 



and Europe, which we have called Syncarida, and 

 which have antennae and tails like shrimps, but the body 



Fig. 249. Gampsonyx fimbnatus of European coal measures, 2!/ 2 times natural 

 size. 



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 Gau- 

 dicliaudi Audouin and Edwards, with the 

 two pairs of antenna? 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 cceca, 

 serving for aerial respiration, thus antici- 

 pating the tracheary system of insects. 

 The nervous system is quite simple. (Fig. 

 250, I(lota>-a, and Fig. 251, that of Serolis.) 

 The digestive canal is straight, consisting 

 of a short oesophagus, a membranous stom- 

 ach, and usually a short tubular intestine; 



v / 



the liver consisting of several short cceca. 

 In Serolis Gaudicltaudi the stomach is somewhat pear- 



