WEST INDIAN STAEFISHES 151 



or spinule-like structures, on a plate, often surrounding a pit or 

 pore. Sometimes two-bladed forceps-like forms occur. 



Bivalve valvular pedicellarige are lacking. Ambulacral feet 

 are generally pointed; sometimes flattened and natatory; rare- 

 ly with a small terminal knob, but without a sucker. 



Ambulacral ampullae are usually double; single in Luidia, 

 Ctenodiscus and allies. Dorsal pore present or absent. Super- 

 ambulacral plates are usually present ; sometimes absent. 



The Paxillosa should only include such groups as do not have 

 true bivalve pedicellariaB nor sucker-feet. The existence of true 

 paxilliform plates on the dorsal surface cannot be made an in- 

 variable diagnostic character, for they occur in some forms of 

 Valvulosa. The development of the ambulacral feet varies much 

 in both groups, and probably depends more on the nature of the 

 bottom anciently inhabited, than on the habits of existing species. 



The gonads are commonly a single pair in the proximal part 

 of the rays, but in Luidia and several deep-sea genera of Astro- 

 pectinidee there is a series along each side of each ray, (multiple 

 gonads.) 



The papulae are confined strictly to the dorsal surface and 

 often to limited or definite radial areas. They are generally 

 simple and stand singly between the dorsal paxillae, protected by 

 the fascioles. In Luidia they become branched. 



In Leptychaster antarcticus the eggs and developing young are 

 carried between the dorsal paxillae, and the young, of some size 

 are attached to the dorsal surface. Some genera are known to 

 undergo a complete metamorphosis, having free swimming larval 

 stages (brachiolaria, etc.) The embryology of most of the 

 genera is unknown. 



Family Astropectinid^ (restricted.) 



Astropectinidce (pars) Gray, Ann. and Mag. Nat. Hist., p. 140, 1840; Sy- 

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

 (includes Luidia). Perrier, op. cit., 1894, p. 193 (pars.) 



AstropectinincB Sladen, op. cit., 1889, p. 175. 



Astropectinidce (sense ext.) Fisher, op. cit., 1911&, p. 37, (Analytical table 

 of all recognized genera). Verrill, op, cit., 1914a, p. 314. 



Paxillosa in which the disk is usually small or of moderate 

 si2:e. The rays are often much elongated. The dorsal surface is 



