SHALLOW-WATER STARFISHES 3O3 



Abactinal plates are more or less paxilliform, parapaxillae or pro- 

 topaxills, with intervening large papular pores on the radial areas. 

 The abactinal plates may bear clusters of more or less elongated 

 spines, or a group of small granules. They usually form obliquely 

 transverse lines on the rays, not always regular. 



Interactinal plates angular, covered either with spines or with 

 granules. Small, simple pedicellaria: sometimes occur on the actinal 

 or abactinal plates. They may have two, three, or four papilliform 

 blades. 



Adambulacral plates usually bear elongated spinules, arranged 

 in three or four small transverse rows ; generally only two or three 

 in the furrow-series; sometimes only one. Dentary plates usually 

 have elongated, acute marginal and apical spines. They are some- 

 times closely united along the median suture; in other cases (Odont- 

 aster) they are separated by a space covered only by membrane. 



The marginal plates are covered either with spinules or with 

 granules, sometimes the upper ones are granulated and the lower 

 spinulose, like the corresponding disk-plates ; they usually have deep- 

 fasciolated sutures. 



Ambulacral feet have suckers. No superambulacral plates. 



Genus Odontaster Verrill. 



Odontaster Verrill, Atner. Joum. Sci., xx, p. 402, 1880; Proc. U. S. Nat. Mus., 

 XVIL p. 262, 1894; Amer. Joiirn. Sci., XLix, p. 136, 1897; op. cit., 1899, 

 p. 205. 



Gnathaster Perrier (pars), Exp. Trav. et Talism., p. 244, 1894. 



Odontaster Bell (f>ars), Proc. Zool. See. London, p. 260, 1893. Fisher, 

 op. cit., 181 1 fc, p. 154. 



A single, odd, hyaline, recurved, movable spine on the apex of 

 each jaw. Dentary plates large, separated by an open, fusiform 

 space, covered by membrane. Abactinal surface covered with ele- 

 vated, convex, or clavate paxilliform plates, or parapaxillae, which 

 usually bear clusters of elongated spinules, like true paxillae; their 

 bases are stellate. Upper marginal plates are usually finely spinu- 

 lated. Lower marginal plates are generally large and placed singly 

 or in the angles around the radial paxillae. The radial abactinal 

 plates form more or less evident obliquely transverse rows and 

 extend nearly or quite to the apical plate. 



The odd interradial marginal plate is usually triangular or wedge- 

 shaped. Simple pedicellariae occur rarely. 



The adambulacral plates usually bear several rows of spines ; 

 usually three or four in the furrow-series, rarely but two. 



