226 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



ules ; no spines except on adambulacral and mouth plates ; abactinal 

 area narrower on raj^s than width of broad, arched superomarginals; 

 abactinal plates compactly placed with usually 6 to 8, but sometimes 

 as many as 12, polygonal crowded gi-anules, or on outer part of ray 

 3 or 4; marginals much broader than long, forming a smooth, evenly 

 rounded margin to ray; actinal intermediate plates restricted to 

 disk and evenly granular; furrow margin slightly convex proxi- 

 mally, decidedly convex distally with 7 to 9 short, stubby spinelets 

 and 12 to 14 compact, polygonal subambulacral granules in 3 or 4 

 longitudinal series; no specialized subambulacral spines; no pedicel- 

 lariae ; adambulacral armature resembling that of Ceramaster. 



Description. — Area of abactinal plates narrower on ray than width 

 of superomarginal plates as seen from above; this narrow band di- 

 minishes in width toward the end of ray very gradually, the abactinal 

 plates reaching the terminal plate. Opposite the fourth superomar- 

 ginal there are 7 longitudinal series of abactinal plates, counting 

 across the ray; opposite the eighth, 5, and opposite the twelfth, 3. 

 This point is about the middle of the ray; the 3 longitudinal series 

 continue to the end, the plates becoming smaller and more closely 

 fitted together. Abactinal plates low tabulate, the tabula being ellip- 

 tical in cross-section and very much narrower than the crown of the 

 few relatively large polygonal, compactly placed granules. These 

 granules are about as high as broad and wider at the top than base. 

 A large radial paxilla has upward of 12. but usually there are only 

 6 to 8, with 1 or none occupying the center; on the outer part of 

 ray there are generally 3 or 4, occasionally only 1 or 2. The usual 

 form for the paxilla crown is hexagonal, but they are not always 

 symmetrical; the largest are on the radial areas. The papulae ex- 

 tend only to the fourth superomarginal, and are distributed all over 

 the disk. 



The plates of the papular areas are nearly circular in general out- 

 line, with 6 short blunt lobes by which they are in contact, or slightly 

 overlap. Outside the papular areas the carinal plates are circular 

 or hexagonal, while the laterals are longer than broad, elliptical in 

 shape, somewhat like half a hexagon. 



Superomarginals, 37 in number, are wide and short, encroach con- 

 spicuously upon abactinal area, and form an arched border thereto; 

 the lateral face is lower than the width of the dorsal, and passes 

 very gradualW into it. Plates covered with a close mail of mostly 

 hexagonal granules, about the size of those of abactinal plates, in 

 5 or 6 not clearly defined transverse series, proximally, becoming 

 reduced distally to 4, 3, and 2. The surface of the plates is smooth 

 and the granules of neighboring plates are fitted so tightly together 

 that no channel is perceptible. Terminal plate, elongate, elliptical, 

 covered with closelv placed granules. 



