CLASSIFICATION 421 



Subclass II. Oligochaeta ( ) 



Order 1. Microdrili ( ) 



Order 2. Macrodrili ( ) 



Class III. Hirudinea ( ) 



Class IV. Onycophora ( ) 



PHYLUM IX. MOLLUSCA 



Class I. Amphineura ( ) 



Order 1. Polyplacophora ( ) 



Order 2. Aplacophora ( ) 



Class II. Gastropoda ( ) 



Subclass I. Streptoneura ( ) 



Order 1. Aspidobranchia ( ) 



Order 2. Pectinibranchia ( ) 



Subclass II. Euthyneura ( ) 



Order 1. Opisthobranchia ( ) 



Order 2. Pulmonata ( ) 



Class III. Scaphopoda ( ) 



Class IV. Pelecypoda ( ) 



Order 1. Protobranchia ( ) 



Order 2. Filibranchia ( ) 



Order 3. Eulamellibranchia ( ) 



Order 4. Septibranchia ( ) 



Class V. Cephalopoda ( ) 



Order 1. Tetrabranchia ( ) 



Order 2. Dibranchia ( ) 



PHYLUM X. ARTHROPODA 



Class I. Crustacea ( ) 



Subclass 1. Branchiopoda ( ) 



Subclass 2. Ostracoda ( ) 



Subclass 3. Copepoda ( ) 



Subclass 4. Cirripedia ( ) 



Subclass 5. Leptostraca ( ) 



Subclass 6. Malacostraca ( ) 



Class II. Merostomata ( ) 



Order 1. Gigantostraca ) 



Class III. Poecilopoda ( ) 



Order 1. Xiphosura ( ) 



