ASTEROIDEA OF NOKTXI PACIFIC AND AD.JACKNT WATERS — FISHER. 217 



CERAMASTER CLARKI Fisher. 

 PI. 38, figs. 3, 4; pi. 58, figs. 2, 2a-b; pi. 59, figs. 6, da. 

 Ceramaster clarki FiBHER, Zool. Anz., vol. 35, March 29, 1910, p. 5.52. 



Diagnosis. — R = .53mm.; r = 33mm.; R=1.6r. General form stellato-pontag- 

 onal, but last two or three superomarginals in contact medially. General aspect 

 somewhat resembling C. patagonicus, but nuirgins much thinner, marginal plates 

 smaller, their granules coarser, hemispherical, and slightly spaced ; the abaci inal plates 

 with fewer and larger granules, more numerous and slightly larger pe<licellarife; 

 the actinal intermediate areas with smaller and less regular plates (especially in 

 the series adjacent to adambulacral-s), and larger, less regular, thimble-shaped 

 granules; adambulacral plates with subequal, robust, truncate, tubercular spinelets 

 in the first actinal series instead of granules, and the plates narrower than long 

 instead of wider than long. 



Description. — The tabula of the abactinal plates are slenderer than in either 

 patagonicus or japonicus and the marginal granules overhang. One to six convex, 

 roundish or faintly polygonal, imequal, spaced granules occupy the center of tabulum, 

 while seven to fifteen more flattened ones occupy the periphery. The latter have 

 a faintly curved or straight beveled outer margin. The edge of the tabulum is not 

 so square cut as in patagonicus, nnd all the granules are larger and more distinctly 

 spaced. Nearl}^ all the tabula have a pincer-shaped pedicellaria with two or 

 three spatulatc or truncate-oblong or even slightly tapering jaws. The figure of 

 the paxillar tabula wnll give a better idea of their structure and appearance than 

 will a description. PapuUc are absent from near tip of ray and from a snuill trian- 

 gular intcrradial area. On this area the plates are abrupth smaller, with very low 

 circular groups of six peripheral and one or no central granules. This difference 

 in the size and spacing of the plates (these being farther apart on the papular 

 areas) is more conspicuous in clarki than in either patagonicus or japonicus. 



The abactinal plates when viewed from the inner or coelomic side are seen to 

 have a very concave under surface. The plates are strongly lobed and the lobes 

 are turned downward, forming the concavity mentioned. The median radial 

 plates have shorter, broader lobes than either adradial series (where the lobes are 

 spatulat« and of unequal length). These lobes appear in many cases to have a 

 suture at the base as if to form incipient independent ossicles. The figure will give 

 a better idea of the form. The high tabula give to the plates of radial areas a 

 decided paxilliform appearance. 



Margin of disk evenly rounded, the plates being small and low, the superomar- 

 ginals forming a roundish bevel. In both series the proxinuil plates are slightly 

 longer than wide, but about the last five or six are wider than long; and the last 

 two or three superomarginals are conspicuously swollen, with most of the surface 

 bare. In one case the last plate is the largest, but usually it is the pemdtimate 

 plate. The distal one to three superomarginals are in contact with their fellows 

 of the opposite side of the ray. These distal five or six plates are larger (with the 

 exception usually of the last plate) than the other plates of the series, which are 

 covered with spaced hemispherical granules. Sometimes one or two pedicellaria^ 



