278 ARTHROPOD A [CH. 



Sub-order i. Podocopa. 



With unbranched second antennae and carapace with 

 entire outline. 

 Ex. Cypris. 



Sub-order ii. Myodocopa. - 



With forked greatly enlarged second antennae and 

 notched carapace. 

 Ex. Cypridina. 



Order 3. Copepoda. 



Small clearly segmented Entomostraca devoid of carapace 

 with long well developed antennae. Four or five pairs of 

 biramous thoracic appendages. 



Ex. Cyclops. 



Order 4. Cirripedia. 



Sessile Entomostraca whose body is not clearly segmented 

 and is enclosed in a carapace strengthened by calcareous plates. 

 Usually five biramous thoracic appendages. Hermaphrodite 

 as a rule. 



Ex. Lepas, Balanus. 



Sub-class B. MALACOSTRACA. 



Large Crustacea as a rule with twenty segments. The ap- 

 pendages behind the gnathites are differentiated into two series, 

 peraeopods and pleopods the region to which the latter are 

 attached being termed the abdomen. 



Order 1. Leptostraca. 



Malacostraca with the carapace in the form of a bivalve shell 

 covering the eight free thoracic segments but not fused with 

 them, abdomen of eight segments, the last two of which do 

 not bear limbs. The telson represented by a caudal fork. 

 Thoracic limbs leaf-like. 



Ex. Nebalia. 



Order 2. Thoracostraca. 



Malacostraca in which the carapace is fused with the 

 thoracic segments and in which the valves of the caudal fork 

 have coalesced to form a telson. Eyes stalked. 



Sub-order i. Schizopoda. 



Thoracostraca with eight pairs of biramous thoracic 

 appendages. 



