1054 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
of Maui, 220-238 fathoms, gray sand; 4096, northeast approach to Pailolo Channel, 272-286 fathoms, 
fine gray sand. 
This Tosia appears to belong to Verrill’ s “Section B. Plinthaster” (op. cit., p. 161), which prob- 
ably deserves recognition as a subgenus. The subgenus is thus characterized: “Pedicellarise with 
narrow blades are present, of small size, about equal to the granules or but little larger. Adambulacral 
plates are wider, about as large as the actinal plates, and bear many crowded spinules; usually 4 to 6 
in the furrow series. Marginal and abactinal plates usually naked in the middle and often areolated. 
Three to five of the dorsal marginal plates are usually in contact medially” (op. cit., p. 161). The 
only modifications to this diagnosis which our species would necessitate is that the pedicellarise are 
decidedly larger than the granules, and adambulacral plates are smaller than adjacent intermediate 
plates. The present species would line up with T. compta Yerrill and T. nitida Yerrill from the West 
Indies, in which pedicellarise occur in both series of the marginal, and on the abactinal plates, and are 
set in special bilobed pits. Upper marginal and abactinal plates are granulated around the edges. 
In our species there are scattered granules on the upper marginal series of plates in addition to those 
around the edges, while there are also pedicellarise on actinal intermediate plates. The special bilobed 
pits are shallow. 
This species is the first of the subgenus to be recognized from the Pacific, the others being Atlantic. 
A fair figure of the general form and appearance of Tosia ( Plinthaster ) perrieri (Sladen) is to be 
found in Perrier, Expeditions Scientifiques du Travailleur et du Talisman, pt. 1, Echinodermes (pi. 25, 
figs, la, lb). Probably Professor Yerrill considers this the type of the subgenus. 
Stellate; rays 5. R=56 mm.; r=29mm.; R=1.93r. Breadth of ray between first and second 
superomarginals, 28 mm. 
General form flat, with a large disk, produced into 5 short rays, which taper evenly from a broad 
base to a bluntly-pointed extremity. Interbrachial arcs very wide and rounded. Abactinal surface 
slightly inflated. Actinal surface subplane. Marginal plates conspicuous but not tumid, forming an 
even border to body. Rays and disk perfectly rigid. Pedicellarise present only on actinal surface. 
The 2 series of marginal plates are not precisely opposite, plate to plate, on ray, but very 
nearly so. The superomarginals, 13 in number from median interradial line to extremity of ray, are 
much broader than high on disk and inner two-thirds of ray, but on outer third of ray the height 
and width become more nearly equal. The abactinal surface of the plates slopes gently off in a sort ! 
of bevel and meets the low lateral face, which is perpendicular. In the interbrachial arc the plates 
are only slightly wider than long, the length very gradually diminishing as they approach extremity 
of ray. Abactinal surface of each superomarginal has a large roundish bare space, the lateral face of 
plate being covered with low roundish granules, which decrease in size toward the margin and likewise 
surround the abactinal naked area in 1 or 2 peripheral series. On outer half of ray the bare space . 
encroaches more and more upon lateral face, until the last 6 plates have only a marginal series of bead- 
like granules. The granules are low and sunk into a very thin membrane, and those of the peripheral 
series are slightly smaller than the others. A small, spatulate, two-jawed pedicellaria is present 
between 2 of the proximal plates. 
Inferomarginals equal the superomarginals in number, but are slightly larger. They are much 
broader than high, encroaching more upon actinal area than do the dorsal marginals upon the 
abactinal. Plates are covered with granules similar to those of superomarginals, there being a small 
round naked area in the center of the actinal face of each, smaller in size than the corresponding 
areas on dorsal series. The outer 3 or 4 plates have only a single series of peripheral granules, the 
general surface being naked. Terminal plate large, short, and armed with a heavy thimble-shaped 
tubercle. 
Abactinal area paved with small, roundish plates compactly placed, small papulae issuing between 
them, except on a limited area in interradial region, where they are absent. Papulae are single, and 4 
Subgenus CERAMASTER Yerrill. 
PI. xxi, fig. 2; pi. xxvi, figs. 4, 4a. 
