426 THE VOYAGE OF H.M.S. CHALLENGER. 
Genus Pholidaster, Sladen. 
Pholidaster, Sladen in Narr. Chall. Exp., 1885, vol. i., p. 616. 
Disk small. Rays long, tapering, subcylindrical and flexible. Interbrachial ares acute. 
Abactinal plates arranged in regular longitudinal series (the median radial series 
largest), bearing large plate-like skin-covered scales, which mask all the plates except 
some of the primary apical plates on the disk and the median radial series along the ray. 
Small isolated papulee are present at the angles of the plates. 
Supero-marginal plates subequal in size to the median radial series of plates, and 
bearing plate-like skin-covered scales similar to those above described. Infero-marginal 
plates smaller than the superior series and bearing a single, delicate, elongate, naked lateral 
spine appressed to the ray, and several compressed, scale-like, skin-covered spinelets. 
Actinal intermediate plates two or three series, each plate bearing a single naked 
spinelet similar to the lateral spine, appressed to the ray, and several skin-covered papille ; 
the large spines forming longitudinal series along the ray. 
Adambulacral plates broader than long, each alternate plate with a prominent ridge 
which extends far into the furrow, the intermediate plates appearing to form the straight 
wall of the furrow. Adambulacral armature consisting of a pair of delicate furrow spines, 
which radiate apart at the inner end of the ridge; on the outer part of the plate is a group 
of skin-covered papille parallel to the furrow. The intermediate non-prominent adam- 
bulacral plates only bear the group of skin-covered papilla, and a few more prominent 
extending to the margin of the furrow. 
Madreporiform body more or less masked by the plate-like scales of the abactinal 
plates ; the striations appear to be few in number and coarse. 
Anal aperture inconspicuous and excentric ; closed by squamiform plates. 
No pedicellariz present. 
Ambulacral tube-feet with a terminal fleshy knob ; crowded and forming four alter- 
nating rows. 
Remarks.—This genus is unquestionably related to Zoroaster, of which it is probably 
the shallow-water representative in this tropical area. Pholidaster is, however, readily 
distinguished from Zoroaster and from all other known forms by the presence of the 
remarkable scales borne on the abactinal and marginal plates. So far as at present known 
the genus has a very small area of distribution. 
Chorology of the Genus Pholidaster. 
a. Geographical distribution :— 
Eastern ARCHIPELAGO: Two species between the parallels of 20° N. and 10° S. 
Pholidaster sywamatus off the Philippine Islands. Pholidaster dis- 
tinctus in the Banda Sea, between the Ki Islands and the Banda Islands. 
