159 



Cartilaginous ring developed only around the calcareous ring. Often 

 very faint or nearly wanting. The holes at the circular canal so large 

 that distinct "tentacle-canals" are visible 13 



10. In each end of body but one size of anchors and plates 11 



In each end of body two different sizes of anchors and plates tualensis 



11. Madreporite short, not elongated along the stone-canal. Calcareous 



ring with distinct projections on anterior margin denticulata 



Madreporite elongated along the stone-canal. Calcareous ring without 

 processes on anterior margin 12 



12. Muscular impressions on calcareous ring distinct, usually not more 

 than three holes in posterior end of anchor-plates. Stone-canal in 



mature specimens often curled into a clue madreporica 



Muscular impressions on calcareous ring very faint or wanting. 

 Usually five small holes in posterior end of anchor-plates. Stone- 

 canal straight psara 



13. Only one sort of anchors and plates; bridge thick and usually 



smooth jolensis 



In posterior end of body two different sizes of anchors and plates; 

 the bridge distinctly dented 14 



14. Tentacles 13, colour finely striped. 5 — 7 small holes in posterior end 



of anchor-plates virgata 



Tentacles probably 14; colour uniformly reddish. 1 — 3 small holes 

 in posterior end of anchor-plates rosea 



15. Colour greyish-green with white stripes. Pl. II fig. 4 albolineata 



Colour varying, not greyish-green with white stripes 16 



16. Colour pure white. In anterior end of body two, in posterior end of 

 body three different sizes of anchors and plates (Fig. 19. 6-9). Anterior 



margin of calcareous ring with distinct projections alba 



Colour varying, only one size of anchors and plates. Anterior margin 



of calcareous ring without distinct projections 17 



17. Colour light, posterior margin of calcareous ring nearly straight 



Fig. 16. 4 recta 



Colour dark, posterior margin of calcareous ring distinctly notched striata 



18. Digits free, not united by a web. West-Indian species. . . . hydriformis 

 Digits united by a web. East Indian species rosetta 



19. Digits united by a web 20 



Digits free, not united by a web 26 



20. Colour pure white, posterior margin of radiais different from that of 



interradiais membrana 



Colour not pure white, posterior margin of radiais not distinctly different 

 from that of interradiais 21 



21. Colour grey with five purple stripes 22 



Colour different, not grey with five purple stripes 23 



22. Radiais and interradiais not distinctly different. Three holes in posterior 

 end of anchor-plates bandae 



