Plate XXI. 

 All the figures on this Plate, except fig. 9, are enlarged. 



1. Schizoporella unicornis, p. 259. 



2. Schizoporella hyalina, p. 266. 



.3. Schizotheca fissa (after Hincks), p. 268. 



4. Hippothoa divaricata, p. 269. 



5. Rhyncopora bispinosa, p. 271. 



6. Lepralia Pallasiana, p. 272. 



7. Lepralia adpressa, p. 274. 



8. Smittia trispinosa, p. 282. 



9. Cellepora ramulosa, nat. size (after Couch), p. 291. 



