EVOLUTION OF THE ECHINODEBMS — FELL 



485 



B 



J 



■A 



Figure 16. — Calyx in crinolds and asterozoans, at comparable early stages of development. 

 A, lateral aspect, and B, dorsal aspect, of Promachocrinus, showing basals. C, corre- 

 sponding calyx in the ophiuroid Ophiosteira. D, E, similar views of the pentacrinoid stage 

 oi Eumorphometra, with suppressed basals, and F, corresponding calyx in the ophiuroid 

 Ophiomastus. G, H, corresponding calyx in the ophiuroid Opkiopyrgus. I, calyx of 

 yound crinoid showing late (postbasal) development of infrabasals. J, K, late (post- 

 basal) development of infrabasals in asteroid Asterina. 



