XII] CLASSIFICATION 277 



Phylum ARTHROPOD A. 



Bilaterally symmetrical Coelomata whose coelom has undergone 

 great reduction and has been functionally replaced by the haemo- 

 coele. The body is divided into segments which are usually 

 arranged in groups. Paired hollow and jointed limbs on some of 

 the segments. 



Class I. CRUSTACEA. 



Aquatic Arthropods usually breathing by gills, with two pairs of 

 antennae. At least three pairs of limbs are changed into gnathites. 



Sub-class A. ENTOMOSTRACA. 



Small, simple Crustacea with varying number of segments. The 

 appendages behind the gnathites form a uniform series. The 

 stomach has no teeth. The larva is a Nauplius. 

 Order 1. Phyllopoda. 



Entomostraca with leaf-like swimming appendages. 

 Sub-order i. Anostraca. 



Long-bodied Phyllopoda without carapace, second 

 antennae converted into grasping organs, eyes stalked 

 (5 or 6 pairs), numerous swimming appendages. 



Ex. Branchipus, Artemia. 

 Sub-order ii. Notostraca. 



Long-bodied Phyllopoda with flattened horizontally 

 extended carapace vestigial antennae and sessile eyes. 

 Numerous swimming appendages. 



Ex. Apus. 

 Sub-order iii. Conchostraca. 



Phyllopoda with bivalve carapace. Enlarged swimming 

 second antennae with ten or twelve pairs of swimming 

 appendages to which the eggs are attached. 

 Sub-order iv. Cladocera. 



Small, short Phyllopoda with bivalve carapace, a dorsal 

 brood-pouch and enlarged swimming second antennae, few 

 swimming appendages. 



Ex. Daphnia, SimocepJialus. 

 Order 2. Ostracoda. 



Small Entomostraca with un segmented bodies. At most 

 seven pairs of appendages. Appendages behind the gnathites 

 leg-like and cylindrical. Body completely enclosed within a 

 bivalve carapace. 



