454 PROCEEDINGS OF THE NATIONAL MUSEUM vol.90 



cular primary plates for a short distance at base of ray imbricate 

 irregularly but over rest of area are joined by smaller and lower sec- 

 ondary plates. These are irregular in shape and imbricate irregularly. 

 Sometimes the end of these plates extend under the large primaries, 

 sometimes they slightly overlap their edges — m short, imbricate. A 

 multitude of small superficial tertiary plates of variable size fortify 

 the joints of the primaries and secondaries and help define the papular 

 pores. These are the same as the superficial platelets of lateral area 

 (fig. 20). 



The exposed surface of the plates is covered by a multitude of very 

 small spinelets with microscopically thorny tips (length 0.22-0.28 mm.) 

 of nearly uniform thickness (0.04-0.05 mm.) on the secondary and 

 tertiary plates, but more robust (0.08-0.12 mm.) on the center of 

 the primaries. 





H/!/ 



m 





Figure 22. — Nepanthia variabilis Clark, X 40: A plate from lateral area near base of ray- 

 to show pedicellaria. PA, papular pore. 



The pedicellariae (fig. 21) of the lateral abactinal plates are rather 

 remarkable. There is a conspicuous pit usually near or at the upper 

 excavate margin of plate. Extending over this are five to eight 

 minutely thorny, sharp spinelets tapering from a rather broad base 

 and conspicuously larger than the other spinelets of plate. They form 

 a U-shaped series or sometimes a circle and resemble the circular 

 spiniform pedicellariae of the Benthopectinidae. The pits probably 

 contain a sense organ. 



I find precisely similar pedicellariae in Nepanthia variabilis Clark 

 (1938, p. 176, pi. 10, figs. 4, 5, pi. 20, figs. 4, 5) from Broome, Western 

 Australia. Nearly every plate of the lateral areas is provided with 

 one, and a scattering of the larger crescentic plates of the abactinal 

 area, are similarly armed (fig. 22). 



