1052 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
slightly shorter than those of adambulacrals, though larger at the inner angle, and tending to become 
prismatic. The actinal surface is beset with 10 or 11 spinelets, 6 of which are a continuation of the 
inner, actinal series of adambulacrals and resemble them. A series of 4 or 5 smaller spinelets runs 
along the suture margin from outer corner of plate, and meets the first series about halfway to the 
inner end. In the angle thus formed 1 or 2 spinelets may be present in large specimens. 
Madreporic body is very small, with a few irregular coarse striations. It is situated at one-fourth 
the distance from center to margin of disk. 
Color in life: Abactinal surface, coral red; actinal surface, whitish. In alcohol, bleached yellow- 
ish, both sides. 
Variations: The chief variation in this species is probably due to age. At any rate the smaller 
specimens have more acute angles to the pentagon, the sides of which show a tendency to become 
incurved very slightly. The number of marginal plates is fairly constantly f. Occasionally 1 or 2 
of the marginals is abnormally divided obliquely or longitudinally. Young specimens show more 
irregularity in the number of marginal plates, since the small distal plate may be absent. One speci- 
men (R=18 mm.) has the following formulas for the 5 sides: f, |, f, f, f; another (R=ll mm.): 
fi t> I) t> I- 
Localities: Type (no. 21162, U. S. National Museum) from station 3919, south coast of Oahu 
Island, 257-220 fathoms, gray sand; bottom temperature, 45.6°. Taken also at following stations: 
4081, north coast of Maui, 202-220 fathoms; 4082, same locality, 220-238 fathoms; 4083, same locality, 
238-253 fathoms; all on gray sand. 
' This species may be readily distinguished by its strictly pentagonal form, by the very massive 
marginal plates, which are few in number (only 3 to a “ ray ” in the upper series) and especially by 
the fact that the distalmost but one of the superomarginals is conspicuously larger than the rest. 
Also the actinal and abactinal plates are granular and bear pedicellarige. Pentagonaster ammophilus 
is very distinct from any other species of the genus, none of which are so regularly pentagonal. In 
the relative sizes of its marginal plates it resembles most nearly P. bourgeti Perrier, although the latter 
has 4 superomarginals to a ray instead of 3, and 2 small plates between the terminal and enlarged 
superomarginal instead of 1, as in ammophilus. 
Genus TOSIA Gray. 
Tosia Gray, Ann. N. H., vol. vi, 1840, p. 281. Type T. australis Gray. 
Astrogoniu m (pars) Muller and Troschel, System der Asteriden, 1842, p. 55. 
Tosia , Gray, Synopsis, 1866, p. 11, pis. m and xvi. 
Pentagonaster (Sec. A, b, pars) Perrier, Revision des StellOrides, 1875, pp. 2C0, 204. 
Pentagonaster (pars), Sladen, Challenger Asteroidea, 1889, p. 264. Perrier, Exped. Trav. and Talisman, 1894, pp. 389, 390. 
Tosia, Verrill, Trans. Conn. Acad., vol. x, 1899, pp. 148, 158. 
Key to Hawaiian species of Tosia. 
a. Abactinal plates naked, bordered by a series of small spaced granules. Pedicellarise conspicuous. 
ceramoidea 
aa. Substellate; abactinal plates small and numerous, covered with granules micropeltata 
Subgenus PLINTH ASTER Verrill. 
Section B . Plinthaster, Verrill, Trans. Conn. Acad., vol. x, 1899, p. 161. 
Tosia (Plinthaster) ceramoidea, new species. 
PI. xvi, figs. 6, 6a; pi. xxii, figs. 3, 4. 
Form pentagonal, flat, slightly prolonged at the angles, where 2 of the marginal plates are in 
contact medially. Sides are fairly straight in fully grown specimen, but in young are decidedly 
incurved. R=36 mm. ; r=25 mm. R=1.44 r. 
Marginal plates are large, but relatively much smaller than in P. ammophilus, and do not encroach 
so conspicuously upon dorsal and ventral areas. Sides of body perpendicular or superomarginal plates 
slightly overhanging inferomarginals. The dorsal and ventral series of marginal plates correspond in 
position — i. e., do not tend to alternate, the suture between the 2 series being nearly straight. There 
are, in type specimen, 14 superomarginals and 16 inferomarginals. Superomarginal plates are slightly 
tumid, about as broad as high, forming a rounded, slightly overhanging edge to the disk. The cord 
