REPORT ON THE ASTEROIDEA. 



263 



1. Form pentagonal, sides distinctly recti- 



lineal. Marginal plates ordinarily 

 few in number 



2. Form more or less pentagonal. Ex- 



tremities of the rays dilated or 

 rounded. Marginal plates few in 

 number ..... 



ii. Marginal plates with tubercles . 

 /S. All plates covered with membrane, and bearing only 

 single, isolated, prominent, obtuse spinelets or elon- 

 gate tubercles. No papulae (?). No pedicellaria 

 y. Actinal intermediate and infero-marginal plates spinu- 

 late, and with small prominent spinelets inter- 

 spersed. Abactinal plates granulose 

 b. Supero-marginal plates united throughout the length of the ray. 

 Abactinal plates confined entirely to the disk. Abactinal 

 plates margined by peculiar valve-like plates. Abactinal 

 plates naked ......... 



b. Abactinal area with paxilliform plates. 



a. Paxillae usually stellate and spinose. Mouth-plates with a pro- 



minent keel, developed aborally into a hyaline spiniform 

 prolongation. Tegumentary covering of the whole test more 

 or less spiniform or papilliform. With odd interradial 

 marginal plates ........ 



b. Paxillae tabulate, bearing granules or papilla usually prismatic 



in form. Mouth-plates not keeled or prominent. No odd 

 interradial marginal plates. 

 a. Paxillae confined to the disk-area. Rays long. Supero- 

 marginal plates uniting in the median radial line, or 

 separated only by a single series of quadrate plates. 

 i. Adambulacral armature arranged in longitu- 

 dinal series. Infero-marginal plates devoid 

 of prominent tegumentary spinelets. With 

 entrenched pedicellariae .... 



ii. Adambulacral armature palmo-radiate and 

 transverse. Infero-marginal plates spini- 

 ferous and with small prominent spinelets. 

 No pedicellariae ..... 



@. Paxillae extending along the ray. Supero-marginal 

 plates separated by several series of paxillae. 

 Small valvate pedicellariae only, and very few in 

 number. 



i. Margiual plates large and conspicuous. Abac- 

 tinal plates small and not developed into 

 large cylindrical tabula. Pedicellariae pro- 

 sent ... .... 



ii. Marginal plates comparatively small. Abac- 

 tinal plates very large, with enormous 

 cylindrical tabula, bearing co-ordinated 

 pranules. No pedicellariae . 



Pentagonaster. 



Asfrogonium. 

 Calliaster. 



Cliitonastfr. 



Callidernla. 



Iconaster. 



Gnathcwtei: 



Nymphailer. 



Paragonasttr. 



M> diastsr. 



Xectria. 



