280 ARTHROPOD A [CH 



Sub-order i. Amphipoda. 



Body laterally compressed. Gills on thoracic appen- 

 dages. 



Ex, Gammarus. 

 Sub-order ii. Isopoda. 



Body dorso-ventrally compressed. The endopodites of 

 some of the abdominal appendages are soft and vascular 

 and act as gills. 



Ex. Asellus, Porcellio, Oniscus. 

 Sub-order iii. Tanaidacea. 



Body uncompressed, abdominal appendages unmodified, 

 two thoracic segments fused with the head, a vestigial cara- 

 pace sheltering one gill. 



Order 4. Syncarida. 



Malacostraca in which the carapace is completely absent 

 but in which the eyes are stalked. The thoracic limbs carry 

 swimming exopodites and branched epipodites. 



Ex. Anaspides. 



Class II. ANTENNATA. 



Arthropoda with a single pair of antennae and with tracheal 

 respiration. 



Sub-class A. PROTOTRACHEATA. [Onychophora.] 

 Soft, caterpillar-like Antennata with numerous pairs of append- 

 ages. Numerous pairs of coelomiducts acting as excretory organs. 

 Ex. Peripatus. 



Sub-class B. MYRIAPODA. 



Antennata, with a head bearing two pairs of jaws well marked off 

 from body, which consists of many similar segments bearing six- 

 or seven-jointed appendages. Excretory organs are ectodermal. 

 Malpighian tubules. 



Order 1. Chilopoda. [Opisthogoneata.] 



Myriapoda flattened dorso-ventrally, bases of legs wide 

 apart : to each tergum corresponds one pair of legs : the 

 segment following the head has a large pair of poison claws : 

 genital opening between the last pair of legs. 



Ex. Lithobius, 



