334 



ARTHROPODA. 



Order 8. Cladoccra* 



9. Phyllopoda. 

 10. Trilobita. 

 11. Merostomata. 



Legion, Branchiopoda. 



Sub -class IV. MALACOSTRACA. 



Division A. EDRIOPHTHALMATA. 

 Order 12. Lcemodipoda.* 

 13. Isopoda. 

 14. Amphipoda. 

 Division B. PODOPHTHALMATA. 

 Order 15. Stomapoda. 

 16. Decapoda. 



Tribe a. Macrura. 

 b. Anomura. 

 c. Bracliyura. 



SUB-CLASS CIRRIPEDIA. 



Animal free ivhen young, lut permanently attached in the 

 adult condition to some foreign body ~by the anterior extremity 

 of the metamorphosed head. The visceral cavity of the adult 



Fig. 196. Morphology of Cirripedia. A, Lepas pectinata, one of the Barnacles, one side of 

 the shell being removed, enlarged four times : c. Peduncle ; d, Cement-duct ; o, Ovary ; s, 

 Ovisac ; v, Vas deferens ; p, Penis. B, Pcecilasma fissa, enlarged five times : c, Peduncle, c, 

 Balamis balanoides, viewed from above, of the natural size. D, Balanus tintinnabulum, with 

 the shell on one side removed to show the animal : a, One of the valves ("scutum ") of the 

 operculum ; 6, Another valve ("tergum") of the operculum. (After Darwin and Pagen- 

 stecher. 



protected ly a calcareous shell of several pieces, or ~by a coria- 

 ceous envelope. Abdomen free and rudimentary. Thoracic seg- 

 ments usually carrying six pairs of forked ciliated limbs. 



