PLATE I 



Fig. I. Austrocidaris canaliculata (A. Agassiz). Adult specimen, carry- 

 ing young ones on the apical system, among the spines. 



Figs. 2-12. Ctenocidaris speciosa, Mortensen. 



2. Specimen infested with Echinophyces ; the spines carrying a number 

 of the bivalve Limopsis sp. Half side view. 



3 . Adult normal specimen, with smooth, spade-shaped oral primaries. 

 Oral side. 



4. Young normal specimen, side view. Some Limopsis on the spines. 



5 . Adult normal specimen, with the spines overgrown by Alcyonidium. 

 Oral side. 



6. Denuded test of normal specimen, side view. 



7. Same of a specimen infested with Echinophyces. 



8. 9. Specimens infested with Echinophyces, side view (8) and aboral 

 side (9). 



10-12. Denuded tests of specimens infested with Echinophyces, 

 showing abnormal position of genital pores, at the edge of the peri- 

 stome in the female (10, 12), in the middle of the interambulacrum 

 in the male (11). 



Figs. 13-15. Eucidaris tribuloides (Lamarck). 



13. Denuded test, oral side, of a young specimen from the West 

 Indies. 



14. Specimen from Ascension, aboral side. 



15. Specimen from Ascension, half denuded. Oral side. 



All figures natural size. 



