ARTHROPODA 



With segmented bodies which are provided with segmented 

 appendages. 



Class 1. Crustacea. 



Usually aquatic. With a more or less hardened 

 outer covering and many thoracic appendages. 

 Subclass 1. Branchiopoda. 



Crustacea with compound eyes; mandibular 

 palp usually absent or vestigial; 4 or more 

 pairs of trunk limbs usually broad and lobed. 

 Some orders of this subclass are: Anostraca 

 (Artemia) ; Notostraca (Apus) ; Cladocera 

 (Daphnia, Simocephalus) . 



Subclass 2. Ostracoda. 



Free swimming with the body inclosed in a 

 bivalve shell; mandibular palp usually bira- 

 mous; not more than 2 pairs of trunk limbs. 

 (Cypris.) 



Subclass 3. Copepoda. 



Free or parasitic; no compound eyes or cara- 

 pace; mandible with biramous, uniramous or 

 no palp; typically 6 pairs of trunk limbs, first 

 pair uniramous, next 4 pairs biramous and 

 sixth pair often uniramous. (Cyclops, Argu- 

 lus, Lernaea.) 



Subclass 4. Cirripedia. 



Comparatively large and usually attached; no 

 compound eyes in adult; forms that are not 

 parasitic covered with calcareous plates; usu- 

 ally 6 pairs biramous, thoracic limbs. (Lepas, 

 Balanus, Chthamalus.) 



Subclass 5. Malacostraca. 



Usually of considerable size; with compound 

 eyes, usually stalked; mandibular palp, if 

 present, uniramous; thorax of 8 segments; ab- 

 domen typically with 6 segments. Some 

 orders of this large subclass are: Leptostraca 

 (Nebalia) ; Hoplocarida (or Stomatopoda) 

 (Chloridella) ; Decapoda (Homarus, Cam- 



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