88 DISCOVERY REPORTS 



marginals nearly twice as broad as superomarginals ; (4) varietal character; in our 

 specimen visible except in interradial arc; (5) there is a high keel and this is indicated 

 in Koehler's fig. i in the two interradii on right; (6) covered as much as in an equal- 

 sized specimen of L. accrescens, in which centre of plate is visible ; (7) extremely variable ; 

 specimen of L. accrescens (R 1 10 mm.) has wider furrows than L. magnificus (R 1 17 mm.) ; 

 see second paragraph above. 



Type locality. Petermann Island, south of Palmer Archipelago, 40-70 m., mud 

 and pebbles. Co-type from Jenny Island, southern end of Adelaide Island, 5 m., 

 pebbles. 



Distribution. Vicinity of Adelaide Island and Petermann Island (McMurdo 

 Strait, Victoria Land, if " Asterias longstaffi" is this species). 



Genus Bathybiaster Danielssen & Koren 



Bathybiaster Danielssen & Koren, Nyt Mag. for Naturvidensk., xxvii, part 4, 1S83, p. 285. Type 

 Astropecten pallidus D. & K. i8jj = Archaster vexillifer Wyville Thomson, 1873. 



Ilyaster Danielssen & Koren, Nyt Mag. for Naturvidensk., xxvni, part i, p. 4. Type llyaster mirabilis 

 D. & K. 



Phoxaster Sladen, Narr. Chall. Exp., i, 1885, p. 611 (no species); 1889, p. 234. Type Phoxaster 

 pwnilis Sladen. 



The north Atlantic Bathybiaster vexillifer (Wyville Thompson, 1873), B^ pallidus 

 (Danielssen & Koren, 1877), and B. robustus (Verrill, 1884), are forms of the same 

 species, which takes the oldest name, vexillifer. 



The circumpolar Antarctic B. loripes ohesus and its warmer water race B. loripes are 

 very similar to B. vexillifer and are subject to a corresponding range of variation. If the 

 southern forms are compared side by side with equal-sized B. vexillifer and vexillifer 

 robustus, it is at once seen that the southern forms have shorter, hence more numerous, 

 marginal plates. Three specimens with R 107 mm. are as follows: B. vexillifer robustus 

 63 marginals. [In typical vexillifer (or pallidus, for which see Danielssen & Koren, 

 1884, pi. 14, fig. i), the marginals are 63 in a specimen with R 107 mm.] B. loripes, 70 

 marginals; B. loripes obesiis, 127 marginals. Another specimen of obesus from the same 

 station (167) with R 140 mm. likewise has 127 marginal plates. 



Probably it is obvious enough that Bathybiaster and Psilaster are very closely related 

 and actually difficult to separate on the basis of the adambulacral armature and the 

 fleshy covering of the actinal intermediate spinelets. The armature of the marginal plates 

 is of no value. In Bathybiaster, however, the abactinal paxillae of the papular area 

 (which excludes a narrow strip along radius) have a 6-lobed or stellate base. The plates 

 imbricate strongly by means of these lobes. The plates of the radial strip are not lobed 

 and are in close contact. In typical Psilaster the abactinal plates do not imbricate nor 

 are they in contact even along the non-papulated radial area of ray ; nor are they lobed, 

 but are circular, polygonal, or elliptical. In the aberrant Psilaster charcoti (least Bathy- 

 biaster-X\kc of any Psilaster) the lateral 5 or 6 plates of a transverse series have about 6 

 slight lobes, of which that on the outer (marginal side) is the largest and touches the 



