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EXPLANATION OF THE PLATES. 



Plate XVIII. 



Fig. 



1. Polypide of Cephalodiscus gilchristi, partly dissected to show the position of 



the parasite Zanclopus cephalodisci in the stomach. One of the gonads 

 of the host is seen immediately above the stomach. 



2. Adult female of Zanclopus cephalodisci, from above. 



3. The same, from the side. The abdomen is generally bent dorsally in the 



position shown here. 



4. Head of adult female, seen from below, a', antennule, a", antenna, mx" , 



second maxilla. Between the bases of the antennules is the deflexed 

 rostrum. 



5. The mouth-cone, more highly magnified. L, labrum or upper lip, I, lateral 



lobe of lower lip, md, mandible. 



6. Abdominal region of adult female, from below ; p^, fifth pair of thoracic feet, 



0, opening of oviduct. 



7. Thoracic foot of second pair ; en, endopodite, ex, exopodite. 



8. Thoracic foot of fourth pair. 



9. Larva of the earliest stage observed. 



10. Third thoracic foot of same ; en, endopodite, ex, exopodite. 



Plate XIX. 



11. Male in fifth Copepodid stage, from above. Appendages omitted. 



12. Head of same, from below ; a' , antennule, showing through the thin cuticle 



the segmentation of the adult stage, a" , antenna, md, mandible, mx" , 

 second maxilla. 



13. Antenna of same. 



14. Abdominal region of same, from below; p^, thoracic foot of fifth pair, g.v., 



genital valve. 



15. First thoracic foot of same ; en, endopodite, ex, exopodite. 



16. Third thoracic foot. 



17. Fourth thoracic foot, 



