2g BULiETIX "6, UNITED STATES NATIONAL, MUSEUM. 



plates are decidedly variable in the number to a ray and in decree of development. 

 Size may also account for the presence of only three terminal plate spinules in 

 Alaskan examples. 



Although these Alaskan specimens present slight differences the totality of 

 characters seems to warrant placing them under tenebrarius. The numerous 

 specimens from the single station sliow greater variation among themselves than 

 do the typical Alaskan and Californian examples, when compared. 



Ymng. — The smallest specimen, from station 2859, has R = 10 mm., r = 5 mm., 

 and eight superomarginal plates, one adambulacral spinelet, segmental papilla-, 

 as such, only on two or three plates, after which they stand over furrow as broadly 

 lanceolate flat spinelets; no superomarginal spinules. The cribriform organs are 

 smaller than in the adult, with about ten lamellse which tend to split up into indi- 

 vidual si)inclets, and the space between the cribriform organs is wider than in adult, 

 about as in Sladen's figure of E. gracilis." Abactinal spuaelets are confmed to the 

 interradial areas, and in fact are scarce on the radial areas of the disk on many 

 considerably larger specunens. 



Type.— Cat. No. 22326, U.S.N.M. 



Type-locality. — Alhatross station 4397, about 200 miles off San Diego, California, 

 2,196 to 2,228 fathoms, on gray mud. 



Distribution. — Southern Alaska to the Galapagos Islands, 1,569 to 2,259 

 fathoms. 



Specimens examined. — Fifty-one specimens from the following stations: 



2859, off Prince of Wales Island, southern Alaska, 1,569 fathoms, gray ooze, 

 bottom tera])erature, 34°. 9 F., forty-five specimens. 



4394, off San Diego, California, 2,259 fathoms, soft gray mud, three specimens. 



4397, about 200 miles off San Diego, California, 2,196 to 2,228 fathoms, gray 

 mud, tliree specimens. Last two stations. Albatross cruise of 1904. 



Remarlcs. — This species is closely related to Eremicaster crassus (Sladen), 

 which was taken b}^ tlie Challenger Expedition in 2,335 fathoms in the South Pacific, 

 midway between Sydney and Valparaiso. From this form tenebrarius differs in 

 having slenderer and (by comparison with figures) longer rays, and about twice as 

 many marginal plates. Eremicaster gracilis (Sladen) from off the western coast 

 of South .jVmerica, between Valparaiso and Juan Fernandez, is probably only a 

 very young specimen of crassus because the differences cited are such as would be 

 expected in a young example. I have already pomted out how tenebranus varies 

 at one station in respect to the superomarginal spinules. It would have not been 

 difficult to have created three species from this collection of forty-five specimens. 

 Ment ion has already been made that in the young of tenebranus abactinal spinelets 

 are developed first on the interradial areas of disk. This would be ecjuivalent to 

 Sladen's phrase "abactinal mend)rane with spinelets confined to limited areas" 

 and is borne out by his figure 1 , on plate 20. The fact is, the species of this genus 

 are more variable than commonly supposed. 



After a careful comparison of specimens of E. tenebrarius with Ludwig's de- 

 scription and figures of E. waltliarii from off Panama and the Galapagos Islands, 



<» Challenger Asteroidea, pi. 22, fig. 3. 



