ANNULOSA: CRUSTACEA. 283 



Distinct respiratory and circulatory organs may be altogether 

 wanting; but, as a rule, distinct branchiae are present. The 

 exact form and structure of the gills differ in different cases, 

 but their leading modifications will be alluded to in treating of 

 the different orders. 



TABULAR VIEW OF THE DIVISIONS OF THE CRUSTACEA. 

 Sub-class I. EPIZOA. 



Order i. Ichthyophthira. 

 it 2. Rhizocephala. 

 it 3. Cirripedia. 



Sub-order i. Thoradca. 

 M 2. Abdominalia. 

 M 3. Apoda. 



Sub-class II. ENTOMOSTRACA. 



Order 6. Ostracoda. \ T . T , 



M 7. Copepoda. j^7^, Lophyropoda. 



H 8. Cladocera. \ 



n 9. Phyllopoda. I Legion, Branchiopoda. 



., i.o. Trilobita. ) 



M ii. Merostomata. 



Sub-class III. MALACOSTRACA. 

 Division A. EDRIOPHTHALMATA, 

 Order 12. Lczmodipoda. 

 M 13. Amphipoda. 

 M 14. Isopoda. 



Division B. PODOPHTHALMATA. 

 Order 15. Stomapoda. 

 it 1 6. De.capoda. 



Tribe a. Macrura. 

 H b. Anomura. 

 it c. Brachyura. 



CHAPTER XXXI. 



SUB-CLASS EPIZOA. 



THE members of this sub-class are Crustaceans which in the 

 adult state (except the males of some forms) are destitute of 

 the power of locomotion, being fixed parasitically to the ex- 



