314 VERRILL 



Ambulacral ampullae single or double. Dorsal pore present or 

 absent. Superambulacral plates usually present ; sometimes absent. 



The Paxillosa should only include such groups as have neither true 

 bivalve pedicellarise nor sucker-feet. The existence of true paxilli- 

 form plates on the dorsal surface cannot be made an invariable 

 diagnostic character, for they occur in some forms of Valvulosa. 

 The development of the ambulacral feet varies much in both groups, 

 and depends mainly on the nature of the bottom commonly 

 inhabited. 



The families represented in shallow water on the Northwest coast 

 are Porcellanasteridae, Astropectinidse, and Luidiidae. See families 

 enumerated on page 283. The only family not represented is Gonio- 

 pectinidae, a deep-sea group. 



Family ASTROPECTINIDSE Gray (restricted). 



Astropectinida (pars) GRAY, Ann. and Mag. Nat. Hist, p. 140, 1840; 



Synopsis, p. 2, 1866. Sladen (pars) Voy. Challenger, xxx, p. 174, 1889 



(includes Luidia). 



AstropectinidcE SLADEN, op. cit., 1859, p. 175. 

 Astropectinidce (sense extended) FISHER, op. cit., I9II&, p. 37- (Analytical 



table of all recognized genera). 



Paxillosa in which the disk is usually small or of moderate size, 

 the rays often much elongated. The dorsal surface is generally 

 covered with highly developed true paxillae (rarely with para- 

 paxillae or pseudopaxillae) , commonly covering fasciolated inter- 

 spaces with intervening simple papulae. 



Both rows of marginal plates are usually large, the inferomar- 

 ginals often the larger. They are either granulated or spinulose and 

 often very spinose, with more or less simple fasciolated grooves 

 between them; not covered by a thick skin. Adambulacral plates 

 usually spinose on the actinal surface and with a divergent row of 

 furrow-spines, without a web. 



Pedicellariae are often lacking; when present usually fasciolate or 

 spiniform, or consisting of two short connivent rows of spinules 

 surrounding a special pore. Ambulacral feet in two rows, large, 

 usually pointed, never with suckers. Ampullae double. Dorsal 

 glands and pore usually present. Superomarginal plates present. 

 Interactinal plates wanting, or more or less numerous in regular 

 simple rows, usually spinulose and with fasciolated grooves between 

 all the rows, but without marginal webs. 



The aproctous condition, formerly supposed to be characteristic 

 of the family, is unreliable, for in nearly all the genera referred to it 



