472 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



a". Siiperomarginal and pi'oximal inferomargiuals without central spine ; lateral 

 plates with prominent spines; carinals with inconspicuous central spine 

 and several enlarged spinelets, or enlarged spinelets only ; pedicellariae 

 small, only slightly longer than width of base; miliary spinelets papilli- 

 form, close-set philippinensis, p. 477. 



fll Carina! and all but distal superomarginal plates without central spine or 

 enlarged spinules ; inferomarginal and lateral plates with central spine ; 

 carinal plates very prominent, subquadrate, arched ; adradial plates in- 

 conspicuous, nearly entirely covered by carinals and superomarginals ; 

 rays very long and slender (R=17 r) ; adambulacral plates with 2 trans- 

 verse series of spines on actinal surface and 1 on the furrow keel of 

 alternate plates; papular pores very small viicroporus, p. 475. 



KEY TO THE INDO-PACIFIC SPECIES OF ZOROASTER.^ 



u\ Carinal, marginal, and lateral plates all with central spine. 

 b\ Carinal plates not unusually large ; pedicellariae conspicuous. 

 c*. R=9 r. Spinelets grooved ; central spine of abactinal plates often ob- 

 solescent: pedicellariae more conspicuous than spines, except those of 

 the 2 lowermost rows; prominent adambulacral plates with 2 large 

 bunches of pedicellariae (12 to 20 to a bunch) deep in furrow. 



alfredi Alcock. 



c^. 11=18 r. Spinelets not grooved ; central spine of abactinal plates well 



developed ; papular pedicellariae very slender, less conspicuous than 



spines, and less numerous than in alfredi; prominent adambulacral 



with a small group of pedicellariae on lowest furrow spine, not 2 



large bunches ophiactis Fisher. 



Ir. Carinal plates not unusually large ; pedicellariae not conspicuous ; sub- 

 ambulacral spinelets not in 2 deiinite transverse series. 

 c'\ R=16 r ; rays hemicylindrical, depressed ; raadreporic body large, tumid. 



conspicuous; carinal spines conical, stout, fluted planus Alcock. 



c^ R=10 to 11 r; rays strongly carinated; madreporic body 6mall. incon- 

 spicuous; carinal spines small, not fluted spinulosus Fisher. 



?>'. Cai-t»nal plates very large, tumid, vertebra-shaped, each with a globular 



or squatly conical^ spine; papular pores very small; adambulacral 



plates with 3 or 4 actinal spines in 2 transverse series, and itroini- 



nent plates with 2 or 3 additional spines in the furrow, the outer with 



1 large pedicellaria, the inner with 6 to 10 small ones^-angulatus Alcock. 



a\ Superomarginal plates without central spine; carinal plates with small 



central spine and several enlarged spinelets, or with tuft of enlarged 



spinelets only. 



» b\ Prominent adambulacral plates with 4 or 5 spines, 1 within furrow with 



1 or 2 pedicellariae; pedicellariae fewer, small; inferomarginal plates 



with central spine carinatus Alcock. 



Ir. Prominent adambulacral plates with 6 or 7 spines; at least 2 furrow 

 spines with pedicellariae, the upper with a pedicellaria as long as spine ; 

 proximal inferomarginal plates without central spine; pedicellariae 



numerous, small philippinensis Fisher. 



rtl Carinal plates without trace of enlarged central spine. 

 b\ Adradial plates conspicuous ; carinal plates medium-sized, oval or rounded, 

 granular ; no superomarginal spines ; R=12 r ; papular pores medium- 

 sized adami Koehler. 



^ Z. tenuis Sladen, from off the north coast of New Guinea, 1,070 fathoms, is too young 

 to compare with these species. It belongs in section a>. 



