172 BULLETIN "76, UNITED STATES NATIONAL MUSEUM. 



A'. Abactinal granules, if present, of usual form, 

 t'. Abactinal plates of normal thickness, not very thin; papulae normal, not few or 

 absent; furrow spinelets not unusually numerous, 

 j'. Abactinal and marginal plates with large spaced granules; adambulacral spines 

 relatively heavy, two in the furrow series, with an enlarged actinal spine; 

 actinal pedicellaria;, with broadly spatulate blades; actinal surface resem- 

 bling Hippnstma Cladaster Verrill, p. 221. 



f. Adambuhicral spines not thick and hea\T; no conspicuously enlarged actinal 

 adambulacral spine. 

 k'. Abactinal plates smooth, at least centrally; pedicellarise when present, 

 bivalved. 

 I'. Abactinal plates strongly stellate, naked centrally, the smooth part con- 

 vex and bordered by one or two rows of bead-like granules; distal 

 superomarginal sometimes enlarged (but never the inferomarginal). 



Tosia Gray. 

 P. Abactinal plates round, small, with a single series of skin-covered granules; 



true bivalved pedicellarise Eugoniaster Verrill. 



P. Abactinal plates flat, smooth, save for some small encircling granules on 

 radial areas; actinal plates granulated; furrow spinelets fairly nu- 

 merous, differentiated, and spaced from actinal adambulacral granules; 



pedicellarije modified bivalved with thin jaws Plinthaslcr Verrill. 



K^. Abactinal plates, as well as actinals, closely granulated all over. 



i'. Abactinal interradial plates not larger than the medioradials; abactinal 

 plates slightly to conspicuously tabulate; general form pentagonal; 

 papulae single, or if more than one to area, then no granules between 

 abactinal plates; actinal row of adambulacral spinelets not conspicu- 

 ously thicker than the marginal series; outlines of plates all distinct. 



Ceramaster Verrill, p. 204. 

 P. Abactinal interradial plates larger than medioradials (carinals); abac- 

 tinal plates strongly stellate, not at all tabulate; whole animal closely 

 granulate, obscuring outlines of plates; papulas one to five to an area; 

 papular areas granulate, bearing sometimes pincer pedicellarise; general 

 form stellate; first actinal row of adambulacral spinelets thicker and 

 more granuliform than the rather slender furrow series; numerous 

 minute bivalved pedicellarise on both surfaces and on marginals. 



Goniodiscaster (young) Clark. 

 f. Abactinal plates very thin, flat, finely granulated but with small central naked 

 area; abactinal integument quite flexible; papulae rudimentary. Many fur- 

 row spinelets Litonotaster Verrill. 



h^. Abactinal granules large, irregular, flat, plate-like; large bivalved pedicellarise 



on both surfaces; no prominent spines Gilbertaster Fisher. 



p. Marginal plates numerous, and superomarginals contiguous, forming long slender rays; 

 abactinal plates smooth. 

 j'. Abactinal, marginal, and actinal intermediate plates smooth, bordered by four- 

 sided granules; abactinal granules flush with surface of plates, elongated, and 

 on radial areas occurring only on longitudinal sutures between the plates; on 

 center of dink and interradial areas they completely surround plates; adambu- 

 lacral plates with about four narrowspines, and behind these, four series graduated 

 to granules; adambulacral armature of the type of Pellaster and Pentagonaster; 

 pedicellarise on ventral surface email, with narrow spatulate blades. 



Jcona«<«r Sladen. 

 g^. Abactinal plates surrounded by small flush granules; marginal and actinal plates 

 with large spaced tubercular granules; actinal plates bordered by bead-like gran- 

 ules; adambulacral plates with largo actinal spinules and divergent furrow series; 

 spatulate, excavate, serrate, "sugar-tongs" pedicellarise Astroceramus Fisher 



