ASTEROIDEA 271 



are irregular in shape and imbricate irregularly. Sometimes the end of these plates 

 extend under the large primaries, sometimes they slightly overlap their edges — in short, 

 imbricate. Very many small superficial tertiary plates of variable size fortify the joints 

 of the primaries and secondaries and help to define the papular pores. These are the 

 same as the superficial platelets of lateral area. 



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 (o-o8-o-i2 mm.) 

 on the centre of the primaries. 



The pedicellariae 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 5-8 minutely thorny, sharp spinelets tapering from a rather broad base and con- 

 spicuously 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 Bentho- 

 pectinidae. The pits probably contain a sense organ. 



I find precisely similar pedicellariae in Nepanthia variabilis^ Clark 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. 



The adambulacral, actinal, and the lateral abactinal plates of Parasterina crassa are in 

 no way different from those of Nepanthia. This leaves only the enlarged plates of the 

 median abactinal area with the numerous intervening secondary plates and superficial 

 tertiary plates upon which to base a new genus. But Parasterina occidentalis Clark 

 (1938, p. 180, pi. 21, fig. 5) has no secondary abactinals. It is questionable, therefore, 

 whether we can place too much reliance for generic characters upon these median 

 abactinal plates. The behaviour of the abactinal plates of Nardoa furnishes reason for 

 caution. In TV. panciforis the plates are numerous, small and most nearly uniform in 

 size. Somewhat larger and progressively more diverse as to size are those of A'^. jnollis, 

 N. tiibercidata and N. novae -caledoniae ; while in N. tiimidosa and iV. frianti the large 

 primary plates are hemispherical and the secondaries small and much more numerous 

 (Fisher, 1919, pis. 108-110). The possibility must be considered that in Nepanthia 

 aberrant species exist with over-developed primary abactinal plates. It is not a rare 

 occurrence in the Asteroidea, and in certain species of the Asteriidae (e.g. Leptasterias 

 polaris, Pisaster ochraceus) is of less than specific value. Both Parasterina crassa (Gray) 

 and P. occidentalis Clark must be regarded with suspicion. I think the former is an 

 aberrant Nepanthia. 



Patiria granifera Gray 



Patiria granifera Gray, Proc. Zool. Sue. Lond., 1847, p. 82, Synopsis, 1866, p. 17. 



Asterina granifera Perrier, 1875, P- 3i9-— H. L. Clark, 1923, p. 281, pi. 17, figs, i, 2.— Mortensen, 



1933. P- 256. 

 St. 90. Simon's Town, False Bay, South Africa, 2-10 fathoms, 2 specmiens (R 50 and 55 mm.). 



1 Clark, 1938, p. 176, pi. 10, figs. 4, 5; pi. 20, figs. 4, 5. 



26-2 



