PALiEOZOIC FOSSILS. 303 



Fig. 9. A part of one ray of Ptilonaster princeps enlarged, showing the 

 ranges of plates, pores, spines etc. : 



d. Limit of the disc ; 

 p. Pore ; 



a. Ambulaeral plate ; 



a, a. Adainbulacral plate ; 



m. Marginal plate with spine attached. 



Fig. 10. Lepidechinus rarispinfs. 

 a. The ambulaeral area ; 



e, a. The interambulacral area; 



c, r. Central range of interambulacral plates. 



At the time this paper was originally published, I intended to procure, 

 if possible, the original specimens of several species described by others, 

 with a view to giving accurate figures of the same, in order that students 

 in Palaeontology, might be able to determine what are, and what are not 

 described forms, as well as to illustrate, and determine the generic charac- 

 ters of some of the doubtful ones. Some of the species here described 

 or noticed will be illustrated in a future Report. 



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