ARISTOTLE'S LANTERN AND I'KHKJNATIIIC CIIMM.K. 



I'.M 



in 



TEXT-PIGS. 217-220. Morphology of radii in Echini. The corona consists of five parts, each including an ambulacrum 

 and two half-interambulacra originating beneath an ocular (pp.35, 43, 62, 86). 



217. Palaeechinus quadriserialis Wright. Lower Carboniferous. Adapted from Plate 30, Tig. 3. X '-' irom 

 the exterior. 



218. Eucidaris Iribiiloides (Lamarck). Bahamas. R. T. J. Coll., 754. X 2.7. Seen from the ini.rinr with thai 

 portion of the lantern and muscles associated with this coronal element (compare lcxt-ti^. 'Jill. 1 



219. Centrechimus setosus (Leske). Florida. R. T. J. Coll., 790. X 1.9. Base of a coronal cli-nifiit arnl that por- 

 tion of the lantern and muscles that are associated with this element (compare text-l'ujs. 21 1. p. Is I; JJ.'i. p. 193). 



220. The same. Face view of the two radial half-pyramids, etc., that are associated with om- i-..ruii:il i-N-nn-ni I..-II.T- 

 ing: ip., interpyramidal muscles; r. p., right half of pyramid '_'. and /. /)., left half of pyramid .'!. 



Letters of text-figs. 218-220 as in text-figs. 221-230 (p. 193). 



