189 



Figure 141; Scaphechinus griseus. Pluteus I stage. 



A — general view of the larva; B — connection between the basal and secondary basal rods. 



Remaining legend same as in Figure 103. 



Figure 142: Scaphechinus griseus. 



Pluteus II stage. Structure of the larval skeleton. 



Legend same as in Figures 107 and 139. 



Pluteus III Stage 



The formation of the skeleton is completed and the fourth pair of arms, 

 the preoral, develops in this stage. Supporting rods inside these arms form 

 from elongated processes of the dorsal arch. As in the preceding species, there 



