PLATE IX— Continued. 

 Ptilonasteb princeps. Hall. 



Page 334. 

 Fig. 9. A part of one ray, showing the ranges of plates, pores, spines, etc. : 

 d. Limit of the disc ; 

 p. The pore; 

 a. Ambulacral plate ; 

 aa. Adambulacral plate ; 

 m. Marginal plate with spine attached. 



Lepidechinus rarispinus, Hall. 



Page 340. 

 Fig. 10. A portion of a specimen showing three ambulacral areas and two interambulacral areas. 

 a. The ambulacral area ; 

 ia. The interambulacral area ; 

 cr. Central range of interambulacral plates. 

 / 



