Mil 



THE VOYAGE OF H.M.S. CHALLENGER. 



ZOROASTERIDiE. 



STICHASTERID.fi. 



a. Abactinal skeleton tessellate, arranged in more or less regular lon- 

 gitudinal series. With intra- and infra-marginal papulae. 

 Primary apical plates persistent in the adult. Marginal plates 

 well developed and always contingent. 



a. Superambulacral plates usually present. Tegumentary develop- 



ments granulate. Pedicellarise (rarely present) ex- 

 cavate LlNCKIID.fi. 



b. No superambulacral plates. Tegumentary developments spi- 



nulate. Pedicellarise (forcipulate) pedunculate. 



a. Adambulacral plates unequal, alternate plates with promi- 

 nent ridges. Adambulacral armature complex, poly- 

 acanthid. Pedicellarise (forcipulate) pedunculate . 



/3. Adambulacral plates small, equal, compressed, with no 

 ridges. Adambulacral armature simple, diplacan- 

 thid. Pedicellarise forcipiform and forficiform 

 b. Abactinal skeleton reticulate, more or less irregular.' With or 



without intra- and infra-marginal papulae. Primary apical 



plates aborted in the adult. Marginal plates feebly developed 



and often separated by intermediate plates. 



a. With no intra-marginal papulae. Adambulacral armature pec- 



tinate. Abactinal skeleton with a more or less highly 

 developed composite spinulation (subpaxilliform). 

 a. With actinal intermediate plates more or less developed. 

 Interbrachial septa present. No supradorsal mem- 

 brane . . SOLASTERID.£. 



fi. No actinal intermediate plates. No interbrachial septa. 

 With a supradorsal membrane forming a more or 

 less perfect nidamental cavity ..... Pterasterid,e. 



b. With intra-marginal papulss. Adambulacral armature isolate 



or grouped, not pectinate. Abactinal skeleton with 



spinelets isolated or grouped, but never composite or 



paxilliform. 

 a. With double interbrachial septa ...... Heliasterid.e. 



fi. With single interbrachial septa. 



i. Actinostomial ring with adambulacral plates promi- 

 nent. Ambulacral tube-feet biserial. 



1. Pedicellarise rarely present, never forcipiform. 



Abactinal skeleton forming an irregular 



o o 



meshwork ...... 



2. With forcipiform pedicellarias. Abactinal skele- 



ton forming a regular quadrangular mesh- 

 work ........ 



ii. Actinostomial ring with ambulacral plates promi- 

 nent. Ambulacral tube-feet quadriserial 

 B. Marginal plates in part aborted altogether, elsewhere represented only 

 by microscopic rudiments. Abactinal skeleton aborted, or present 

 only on the disk and ovarial regions. Parambulacral and inter- 

 mediate actinal plates altogether absent. No interbrachial septa. 

 Spinelets in sheaths clothed with pedicellarias ..... Brisingidj:. 



EcHINASTERIDa;. 



Pedicellasterid^. 

 asteriid,£. 



