206 BULLETIN 16, UNITED STATES NATIONAL MUSEUM. 



KEY TO THE SPECIES OP CERAMASTER HEREIN DESCRIBED. 



a'. A well-defined more or less triangular interradial area tree from papulae; papulae single; interradiai 



abactinal plates never lobed; furrow spinelets four or more. 



fc'. Furrow spinelets numerous, six or more proximally; abactinal tabula well spaced, rather convex. 



witli many small crowded granules, of which the marginal series is sensibly smaller. 



c'. No abactinal secondary plates; actinal intermediate granules flat and closely crowded; furrow 



spinelets about six proximally; margin of disk typically thicker; pedicellarise low, bivalved. 



japonicus, p. 206. 

 (P. Secondary abactinal plates on radial areas; actinal intermediate granules well spaced, bead- 

 like; furrow spinelets seven or eight proximally, slender; disk very thin and margin thin; 



pedicellarise with short spatulate jaws leptoceramus, p. 210. 



fc'. Furrow spinelets usually not more than five; proximally abactinal tabula closer, with larger, fewer 



granules, the marginal granules being equal to or larger than the central ones. 



c'. Superomarginal plates usually with a tumid bare spot; the granules small and crowded, forn>- 



ing a smooth pavement; abactinal tabula with numerous central granules; adambulacral 



plates proximally as wide as long and first actinal series not enlarged into conspicuous stubby 



tubercular spinelets patagonims, p. 214. 



c'. Superomarginal plates small, only a few distals with a tumid bare spot, their granules coarse 

 and hemispherical; abactinal tabula with few granules; adambulacral plates proximally 

 narrower than long, with four long furrow spinelets and a series of actinal spinelets. 



elarki, p. 217. 



a'. Papulae distributed all over abactinal surface, usually two to tour in a group; all abactinal plates 



lobed; furrow spinelets two or three; adambulacral plates very short, more than twice as wide 



as long arcticus, p. 219. 



CERAMASTER JAPONICUS (Sladen). 



PI. 37, figs. 1-3; pi. 59, fig. 3. 



Pentagomaslcr japoniciis Sladen, Challenger Asteroidea, 1889, p. 272, pi. 46, figs. 1 and 2; pi. 



49, figs. 1 and 2. 

 Mediaster japonicus Verrill, Trans. Conn. Acad., vol. 10, 1899, p. 179. 



Diagnosis. — One of the largest if not the largest species in this or any closely 

 allied genus. 11 = 102 mm.; r=65 mm.; R = 1.56 r (varying to E=1.36 r). Gen- 

 eral shape pentagonal or arcuate pentagonal, depressed, the edges of body more 

 or less thickened; abactinal surface usually swollen on the radial areas; actinal 

 surface nearly plane. Abactinal surface covered with fairly regular, spaced, 

 hexagonal to ({uadrate tabula crowned with a convex group of numerous polygonal 

 granules, the marginal series regidar, sometimes compressed, and when dried show- 

 ing a pit in the toj). On the interradial areas tabula are quadrate and smaller. 

 Many of the tabula with a bivalved pediceUaria, having tlain, lameUiform jaws 

 which are wider than liigh. These vary in size, equaling one-third or one-fourth 

 the width of the tabulum. Marginal plates variable, covered with small flat crowded 

 granules, for m ing an evenly rounded, or a decidedly tumid margin to ray; a bare 

 space sometimes present on plates of both series, each superomarginal, \vith one 

 to four small bivalved pedicellarise, whose thin jaws equal two to four granules 

 in width. These arc situated usually on the abactinal surface of the superomar- 

 ginals near the margins; inferomarginals with usuaDy only one pedicellaria or 

 none. Actinal intermediate areas very extensive, the plates decreasing in size 

 toward margin, and covered with crowded low flat polygonal granules, of wliich 

 the marginal are slightly the largest; individual plates perfectly flat and vari- 



