ASTEKOIDEA OF NORTH PACIFIC AND ADJACENT WATERS — FISHER. 239 



four) to an ossicle. The papulae are scattered abundantly among these o.s.sicle3. Tiie 

 figure will show more clearly the arrangement of the dorsal plates. 



Superomarginal plates rather small, irregularly f|uudrilateral, higher than long 

 in middle of interbrachial arc, but longer than high throughout most of ray except 

 at tip. On account of the inflation of the abactinal surface these plates are mostly 

 confined to side of ray, and the abactinal edge of each is arched. Each plate is 

 tumid and bears in the center a rigid acorn-shaped or conical tubercular spine 

 sUghtly larger than those of the median radial series. The general surface of plates 

 is covered with polygonal granules similar to those of abactinal surface, the periph- 

 eral granules being elongated and a number on each ])late convex or low. The 

 granules are attached by nearly the entire under surface, there being very Uttle 

 free edge. Superomarginals twenty-six or twenty-seven in number from median 

 interradial line to extremity of ray. Inferomarginals slightly larger, and more 

 nearly scjuare on the ray where the upper series is oblong. In general each infero- 

 marguial corresponds to a superomarginal and is similarly covered with granules 

 (most of which, exclusive of the peripheral series, are prominent or subconical). 

 Each bears one or two, rarely three, tubercular spines in the center, all short and 

 stubby. Smaller plates intercalated here antl there in the inferior series are aj)par- 

 entlj- due to injury of some sort. 



Adambulacral plates nearly scfuare, each bearing two large, heavy truncate 

 furrow spines, u.sually compressed at tip. Sometimes the tip is conspicuously 

 widened and occasionally grooved or even incipiently bifid or trifid. A large sessile 

 bivalved i)edicellaria occupies the furrow margin of first plate, extending the whole 

 length of plate; a similar pedicellaria occurs frec(uently on other plates of the series 

 but there is no regularity of occurrence. On actinal surface of each plate is a 

 robust sjjine just beliind the fiuTow spines, which it greatly resembles, though a 

 trifle shorter; this spine is either bluntly tipped, compressed, or curiously wrinkled. 

 It is reduced to a small conical tubercle, a mere specialization of one of the granules, 

 on those plates in which a pedicellaria replaces the furrow series. General surface 

 of plate is covered with irregulur platc-hke granules similar to those of the actinal 

 intermediate plates. 



Mouth plates fairl}' large. Furrow spines three, flattened, the inner flaring 

 and hatchet-like, though irregular; an odii spine at inner angle of the combined 

 plates; one much smaller spine on actinal surface adjacent to outt'r furrow spine; 

 surface of plate covered with two longitudinal (interradial) rows of flattened plate- 

 like granules wliich diverge and partially surround the actinal spine, being much 

 smaller towanl the inner angle; the.se granules are cjuailrate or pentagonal, and 

 their surface sunken a trifle, then raised in a small low boss in the center. The 

 actinal spine may be absent. 



Actinal interradial areas large; a single row of intermediate j)lates extending 

 verj' nearly to tip; a secoml series two-thirds the length of the ray; a third very 

 nearly as far; a fourth nearly half, and so on. Phitos adjacent to adambtdacrals 

 largest, elongated transversely, and more regular than the others, though far from 

 regular themselves; most of them bear a long bivalved sessile pedicellaria (4 mm.) 

 not more than O.n mm. liigh. placed transversely or obli(|uely transvi'rscly. forming 

 a very conspicuous series uti I'iili.T siil.- .if the adarnbulncrnl plates ami extending 



