ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WAILK — ) l.-ll LH. 251 



Order SPINULOSA Perrier. 



PediccUiiriiT rare, never forci])if(irm; abactinal skeleton reticulate i>r imbri- 

 cated, sometimes absent; abactinal spines always present ami usually numerous, 

 isolated, in groups, or forming regular fascicules and jjseudopaxillffi; marginal plates 

 usually inconspicuous; papula dorsal only or also intramarginal and actinal; 

 ambulacra! plates not crowded and compressed; actinostome with adambulacral 

 plates prominent; tube feet with well ileveloped sucking disk, and usually biserial; 

 mouth plates medium-sized or large. 



Tills order is poorh' defined as regards its limits toward the Phanerozonia, but 

 is sharply separated from the Forcipulata by the absence of the characteristic 

 forcipiform pediccllarise of the latter. Certain of the Asteropidse have been 

 regarded at different times by Perrier as a part of the Asterinidse, or as constituting 

 a separate family, the Poraniidse. The entire order Velata of Perrier has been 

 merged with the Spinulosa. 



The Asteropitia? contain forms wliicli are not very different from the Gonias- 

 teridffi and other genera which show decided relationships with the Spinulosa. 

 The family is therefore in a measure transitional. The Ganeriidae are also some- 

 what intermediate, but appear to be nearer the Asterinidaj and Echinasteridse, 

 although the marginal plates are phanerozonid. 



The Cr\-ptozonia of Sladen includes, besides the families here assigned to the 

 Spinulosa, all the Forcipulata and the Linckiidsp, and lacks the Ganeriidae and 

 Asterinidae, wliich were relegated to the Phanerozonia. The Linckiitlae are nearer 

 the Gomasteridaj than are the Asterinida', but it will jirobabh- long be a matter 

 upon which opinion will differ as to whether the Asteropida? is a natural family. 

 Sladen's arrangement of liis cryptozoniate families is certainly unnatural. The 

 placing of the Zoroasteridae and the Stichasteridac next to the Linckiida> and far 

 removed from the iVsteriida; has uotliing to recommend it. The Forcipulata is 

 probably the best defined of all the orders, as its families have less in common with 

 the Spinulosa than have those of the Phanerozonia. 



If the families constituting the Phanerozonia are first removed, then the For- 

 cipulata segregated, the remainder will bo the assemblage constituting the Spinu- 

 losa — an order not difficult to recognize but decidedly difficult to adequately 

 characterize. 



KEY TO THE KNOWN FAMILIES OK SPINULOS.I. 



a'. Mouth plates rather Hmall, not spade-shaped or [ilowshare-shaped ; amhulaoral furrows narrow. 

 6'. Mar^^inal plates large and phanerozonid in character; abactinal skeleton imbricated or reticulated 

 actinal plates regularly arranged in rows extending from adambulacrals to marginals and bear- 

 ing one or two large spines or small groufxsof spinelets Ganeriidx^ 



b-. Marginal plates inconspicuous, 

 c'. Abactinal skeleton well developed, not wholly aborted. 



(/'. Abactinal skeleton formed of closely imbricating plates bearing small spines; actinal ekeleton 

 formed of imbricating plates bearing a tuft or fan of spinelets AsterinicUe, p. 263. 



<> Comprises Ganeria, LebruiuisUr, Vycelhra, RadituUr, and ScotiatUr. 



