AKT. 6 A NEW SEA STAR FISHEB 6 



The siiperomarginal spines are similar in form to the abactinal 

 spines (followinfi: the variation of the latter) and are generally 

 slightly smaller. Typically they stand one to a plate, close together, 

 forming a very well-defined series, characteristically high on the 

 side of the ray, so that the proximal half, at least, and sometimes 

 the whole ray, is bordered, when viewed from above, by the infero- 

 marginals, or by the first series of actinal spines. This character 

 is accentuated in small examples (R 110 mm.), in which the abac- 

 tinal area is narrow. Interradially the siiperomarginal series extends 

 half way to the center of the disk. Two or three spines occur on 

 the plates of the proximal half of ray in specimens from stations 

 4796, 3235, and 3291 (1 each). 



There is a wide intermarginal channel (2 or 2.5 times length of 

 inferomarginal spines). Inferomarginal spines similar to supero- 

 marginals, but a little longer (3 or 4 mm. in giant specimens), some- 

 times one to a plate, sometimes two, or rather irregularly one and 

 two proximally and one distally. The series bends upward inter- 

 radially, and in some specimens is abactinal (or dorsolateral) in 

 position. 



In large specimens there are six series of spiniferous and one 

 short series of spineless actinal plates at the base of the ray. There 

 is considerable variation in the number of spines to the plate. All 

 plates may be monacanthid. In this case there are eight regular, 

 spaced longiseries of spines, of which two are marginal series abac- 

 tinal in position (station 3282). The outer three or four series are 

 sometimes regularly or irregularly diplacanthid and the inner two 

 or three monacanthid; or the outer row may be monacanthid, the 

 next two irregularly diplacanthid, and the remaining three, mona- 

 canthid (station 3281). In a specimen from station 2842 a con- 

 siderable number of plates are triplacanthid. In large specimens 

 the sixth or inner series of actinal spines extends one-third R meas- 

 ured from center of disk. The actinal spines become gradually a 

 little longer, sometimes heavier and clavate, in passing from the 

 outer toward the inner series. The details of the actinal spines are 

 variable, as in other species. The tips may be compressed and sub- 

 truncate, silicate, or tapered, blunt, or pointed. The smallest speci- 

 men (station 3650) with R 46 mm., has four series of actinal plates. 

 The larger specimen from Kamchatka (station 4796) with R 265 

 mm. has but five series of actinal plates. Whether this is constant 

 for large Asiatic examples can not be determined. 



The actinal channels are typically well marked, even broad in 

 some cases, so that the rows of spines are distinct and separated. 



The adambulacral plates are triplacanthid and diplacanthid. In 

 large examples most of tlie plates of the proximal half of the ray 



