122 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 
edge of the test. The plates of the frontal ambulacrum below the 
fasciole are narrow and naked. There are three well-developed (? 
penicillate) tube feet to each side of the episternum. Phyllodes little 
developed; the three first plates of the anterolateral ambulacra with 
penicillate tube feet. 
The anterolateral and the posterior interambulacra form rather 
sharp keels, less so the posterolateral interambulacra. The sternum 
is moderately broad, narrowing anteriorly; the tubercles continue to 
the anterior end, where the sternum meets the posterior prolongation 
of the labrum, which does not pass beyond the end of the first adjoining 
ambulacral plates. The labrum forms a prominent lip with reversed 
edge. Peristome small, 6 mm. broad, 3 mm. long; the mouth opening 
large; the peristomial membrane contains only small, rounded plates, 
which are not contiguous. The first interambulacral plates are 
broadly in contact with the peristome. The apical system is distinctly 
posterior, 28 mm. from the anterior, 20 mm. from the posterior end. 
The madreporite does not extend beyond the posterior ocular plate, and 
the madreporic pores are confined to the part between and a little 
anterior to the two large genital pores. The periproct, which is 
situated at the upper edge of the concave posterior end, is round or 
irregularly oval; the anal opening is nearer the lower edge, the 
periproctal plates at the upper edge being the largest. 
The very conspicuous peripetalous fasciole bends only slightly in- 
ward between the petals, the latero-anal fasciole distinct only as a 
straight line below the periproct. 
The globiferous pedicellariae I have found only on the aboral side, 
in the petals and in the frontal ambulacrum; the valves terminate in 
a single tooth. The other pedicellariae are not peculiar. Ophicephal- 
ous pedicellariae are not found on any of the specimens at hand. 
The color, which is well preserved on the type specimen, is dark 
brownish on the aboral side in the anterior part but gradually fades 
behind the peripetalous fasciole, the posterior part being whitish. On 
the oral side the same dark color is found also at least in the posterior 
part of the sternum. The peripetalous fasciole is also dark brown 
and very conspicuous. In the specimen from station 5469 the aboral 
side is more light brownish, and no dark color is found on the sternum. 
Remarks.—It seems evident that this species is nearly related to 
Hypselaster fragilis H. L. Clark; it bears particularly a considerable 
likeness to the specimen figured in his Catalogue of the Recent Sea- 
urchins of the British Museum, plate 11, figures 1-3, and one might be 
tempted to regard it as identical with that species. However, it differs 
from fragilis in the important character of the apical system being 
distinctly posterior, whereas it is central or anterior in fragilis. Fur- 
ther, in the analysis of the test given in Clark’s Hawaiian and other 
Pacific Echini, Echinoneidae . . . Spatangidae plate 148, figure 8, the 
