ASTEROIDEA OF NORTH PACIFIC AND ADJACENT WATERS FISHER 9 



pedicellariae; adambulacral plates short and broad, with proximally usually two 

 aboral furrow spinelets and two subambulacral spines all in a transverse series, and 

 sometimes also a furrow spinelet on the proximal half of plate; first 10 or 12 outer 

 subambulacral spines with circular, enlarged, sharply truncate tip; mouth plates 

 decidedly small, with two or three actinostomial spinelets, and on the outer part of 

 plate a transverse series consisting of one or two adoral furrow spinelets and one taper- 

 ing suboral spine; first 2 or 2.5 adambulacral plates of each ray fused to those of 

 adjacent ray by a nonmuscular articulation. R 220+ mm., r 15 mm. (14 rays); 

 R 245 mm., r 13 mm. (12 rays). 



Description. — Disk fairly large and elevated above base of rays as a rule, the 

 margin being rounded. Abactinal surface plane, covered with terete, papilliform, 

 blunt, uniform, skin-covered spinelets which are sharp when dried, and spaced about 

 0.5 mm. apart. The calcareous part of the spinelet is quite slender, about 1 mm. 

 long, and the tip is provided with numberous microscopic points. The abactinal 

 plates of the disk are subcircular with irregular margin and the spinelets are ordinarily 

 one to a plate, although a few plates near the border have two to six spinelets in one 

 or two rows. There are no pedicellariae among the spinelets. In among the ordinary 

 plates are small irregular spineless plates, one-fourth to one-half the diameter of the 

 primary plates. The larger plates with several spinelets probably represent the 

 primary apical plates. 



Genital region of ray very long, equal to 8.5 to 10 r, or on the only complete 

 ray of an adult specimen about 0.6 the length of the ray. 



The costae are somewhat irregular in spacing and form. Ordinarily they are 

 opposite alternate (short) adambulacral plates with intervals where they correspond 

 to two or three consecutive adambulacral plates. The arches are typically brisingoid 

 in being composed of compressed plates so that they form an elevated ridge, which is 

 ordinarily sinuous on the mid-dorsal region, and frequently incomplete in the mid- 

 dorsal region as that part of the arch may be suppressed. Sometimes the arches 

 branch and join the adjacent arches. At the base of the ray the ridges vary greatly 

 on different rays of the same specimen, there sometimes being only disconnected 

 plates. These are present, more or less, on the dorsal region when the arches are 

 incomplete. The costae and independent plates bear a single series of conspicuous 

 spinelets, 0.75 to 1.25 mm. long, and numerous slender pedicellariae. There are 35 

 to 40 complete and incomplete arches reaching 0.6 to 0.7 the length of rays or 8 to 

 10 r from base of ray. 



Lateral spines long, except the first few; first spine at upper border of fifth or 

 sixth adambulacral plate. The succeeding spines increase rapidly in length; about 

 4 r from base they are five adambulacral plates, or 10 to 11 mm., in length, and 

 very slender. 



Adambulacral plates shorter than broad at base of ray, and only slightly longer 

 than broad throughout the remainder of genital region. Armature consists of a 

 transverse series, along the aboral margin of the plate, of two spinelets and two 

 spines, or beyond the base of the ray, one spinelet and two spines. The spinelets are 

 about as long as the plate, or a little longer, and are directed into the furrow. They 

 are incased in a loose sacculus bearing small pedicellariae. The outer of the two 

 large subambulacral spines is heavier than the inner and the first 10 or 12 are shorter 



